Ruby On Rails 3

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The contoller should hand off heavy code to...

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the model

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How many ways can controller create http responses?

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3 - render, redirect, head

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By default, controllers in Rails automatically render ...

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views with names that correspond to valid routes.

e.g. resources :books -> /books/ -> index

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Will this work to render an index page?
def index
@books = Book.all
end

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Yes we have convention over configuration, in that there is no explicit render at the end of this index action. The rule is that if you do not explicitly render something by the end of the controller action, rails will look for the action_name.html.erb template in the controllers view path and then render that,

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If you want to see the exact results of a call to render without needing to inspect it in a browser, you can call
.....

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render_to_string

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What does response 200 ok mean?

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the request was successful

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How do you change the http resonse for a request?

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set the :status options on render to change this response

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How do you render the view that corresponds to a different action within the same template?

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call render with the views name
def update
if @book.update_attributes(params[:book])
else
render "edit"
end

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Render accepts symbols or strings

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both
render "edit" and render :edit both work

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Do you need to use render with the :action option
render :action => "edit"

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NO - not in rails 3 - the string or symbol is enough

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Does render a specified action run the code in the controller? action in the controller.

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No specified action is used to determine which view to render, but Rails does not run any of the code for that

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How to render an Action’s Template from Another Controller

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You can also do that with render, which accepts the full path (relative to app/views) of the template to render.
render 'products/show'


same as render :template => 'books/edit'

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Rendering an Arbitrary File e.g. a view that’s entirely outside of your application (perhaps you’re sharing views between two Rails applications)

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render "/u/apps/warehouse_app/current/app/views/products/show"

same as the file option
:file => "/u/apps/warehouse_app/current/app/views/products/show"

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What does this do?
render :inline => "<% products.each do |p| %><p><%= p.name %><p><% end %>"

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The render method can do without a view completely, if you’re willing to use the :inline option to supply ERB as part of the method call.

here is seldom any good reason to use this optio

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How to render javascript-based page updates inline in your controller?

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render :update do |page| page.replace_html 'warning', "Invalid options supplied" end

use rjs instead

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How to send plain text – with no markup at all – back to the browser

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render :text => "OK"
useful most useful when you’re responding to AJAX or web service requests that are expecting something other than proper HTML.y

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How to render in json

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render :json => @product

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Do you need need to call to_json on the object that you want to render. If you use the :json option

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no - called auto by render :json

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How to render xml

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render :xml => @product

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Where does Rails look to fnd the current layout,

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Rails first looks for a file in app/views/layouts with the same base name as the controller.

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How to override the automatic layout conventions in your controllers

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class ProductsController < ApplicationController

layout "inventory" #...
end

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How to To assign a specific layout for the entire application,

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class ApplicationController < ActionController::Base l

ayout "main" #...
end

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How to dynamically choose a layout at runtime

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class ProductsController < ApplicationController

layout :products_layout

def show @product = Product.find(params[:id])
end

private
def products_layout @current_user.special? ? "special" : "products" end

end

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`how to pass layouts either a method name or an array of method names which correspond to method names within the controller to inclue / exclude

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:only and :except options
layout "product", :except => [:index, :rss]

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Rails will start the rendering proces does this stop the rest of the code in the action from running

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No - thus if another render is called “Can only render or redirect once per action” is thrown

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“Can only render or redirect once per action” - is this ever thrown due to the implicit render?

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no - it detects if render has already been called

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best practice conditional rendering (1 condition, otherwise default)

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def show
@book = Book.find(params[:id])
if @book.special? render :action => "special_show"
end
end

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What does the redirect_to method do

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it tells the browser to send a new request for a different UR

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special redirect that sends the user back to the page they just came from:

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redirect_to :back

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HTTP status code .... when you call redirect_to. I

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302 (temporary redirect)

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what is the speed issue with redirect_to?

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it requires a round trip to the browser
added latency

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Idea to overcome added latency when redirecting

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Prepare the passed variables and render instead

def show
@book = Book.find_by_id(params[:id])
if @book.nil?
@books = Book.all
render "index", :alert => 'Your book was not found!'
end
end

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how to link to js files

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javascript_include_tag

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where does javascript_include_tag look by default

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public/javascripts f

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How to To include public/javascripts/main.js and public/javascripts/columns.js:

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<%= javascript_include_tag "main", "columns" %>

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what is the speed issue with redirect_to?

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it requires a round trip to the browser
added latency

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Idea to overcome added latency when redirecting

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Prepare the passed variables and render instead

def show
@book = Book.find_by_id(params[:id])
if @book.nil?
@books = Book.all
render "index", :alert => 'Your book was not found!'
end
end

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how to link to js files

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javascript_include_tag

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where does javascript_include_tag look by default

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public/javascripts f

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How to To include public/javascripts/main.js and public/javascripts/columns.js:

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<%= javascript_include_tag "main", "columns" %>

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How to load all js files, including those in subfolders of public/javascripts as well:

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<%= javascript_include_tag :all, :recursive => true %>

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how to combine js files into one (faster)

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<%= javascript_include_tag "main", "columns", :cache => true %>

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javascript_..._tag
stylesheet_..._tag

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include
link

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where does stylseheet include tag look by default

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public/stylesheets

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do you need to specify .css / .js with their include/link tags

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no - just a string of their file name - e.g. main.css "main"

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what is the default media type of stylehseet_link_tag

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media="screen"

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how to specify a media type with stylesheet-Includ_tag

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%= stylesheet_link_tag "main_print", :media => "print" %>

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how to inks every CSS file in public/stylesheets:

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<%= stylesheet_link_tag :all %>
, :recursive => true for subfolders

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how to link to an image in public/images

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<%= image_tag "header.png" %>
default dir is public/iages

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for image_tags do you need to specify the extension

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yes - new to rails 3 - error if no extension given

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How to add html options with image_tag (e.g. for height)

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<%= image_tag "icons/delete.gif", {:height => 45} %>
must be in a prop => value hash

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with image_tag how do you supply an alternate image to show on mouseover:

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<%= image_tag "home.gif", :onmouseover => "menu/home_highlight.gif" %>

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if you do not specify an explicit alt tag, image_tag defaults to ..

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the file name of the file

override with
<%= image_tag "home.gif", :alt => "My Lovely Home" %>

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whats a handy way to specify an images size with image_tag

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<%= image_tag "home.gif", :size => "50x20" %>

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how to specify class or id of an image_tag

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<%= image_tag "home.gif", :alt => "Go Home", :id => "HomeImage", :class => 'nav_bar' %>

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how to inclue a HTML 5 <video> in rails

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<%= video_tag "movie.ogg" %>
relative to the public/videos

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does the video_tag have the specify the :size => "#{width}x#{height} like image_tag

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yes it sure does

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starts playing the video on page load. viedo_tag

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# :autoplay => true,

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loops the video once it gets to the end viedo_tag

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:loop => true,

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image to put in place of the video before it starts playing. viedo_tag

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:poster => 'image_name.png', provides an

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provides browser supplied controls for the user to interact with the video

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:controls => true

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link to an mp3 (

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<%= audio_tag "music.mp3" %>

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where audio_tag looks for mp3s

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public/audios.

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Within the context of a layout, yield identifies?

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a section where content from the view should be inserted.
<body> <%= yield %> </body>

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multiple yielding regions: how

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<%= yield :head %> as well as regular <%= yield %> elswhere (referred to as unnamed yeild)

now use a <% content_for :head do %> <title>A simple page</title> <% end %>

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You only use content_for to insert content in

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named yields

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content_for is useful for

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load page-specific javascript or css files into the header of an otherwise generic layout.

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how to partial as part of a view

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<%= render "menu" %>
This will render a file named _menu.html.erb at that point within the view being rendered.

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partials could contain content that is

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shared among many pages in your application.

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For content that is shared among all pages in your application, you can use partials directly from

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layouts.

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How to use partial layouts

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<%= render "link_area", :layout => "graybar" %>
render it using the layout _graybar.html.erb.

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syntax for passing variables to partials

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:locals => { :zone => @zone }

view has @zone
partial gets zone (e.g. %= form_for(zone) do |f| %> <p> )

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Every partial also has a local variable with the same name as the.....

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partial (minus the underscore).

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what does this doe <%= render :partial => "customer", :object => @new_customer %>
_customer partial

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Within the customer partial, the customer variable will refer to @new_customer from the parent view.
[since every partial has a local var with sme name as partial]

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If you have an instance of a model to render into a partial, you can use a shorthand syntax:

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<%= render @customer %>
will use _customer.html.erb to render it and will pass the local variable customer into the partial

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how to set it so the partial will be inserted once for each member in the collection:

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<%= render :partial => "product", :collection => @products %>

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What should you be aware of when rendering collections of partials

<%= render :partial => "product", :collection => @products %>

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the individual instances of the partial have access to the member of the collection being rendered via a variable named after the partial.
he partial is _product, and within the _product partial, you can refer to product to get the instance that is being rendered.

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Shorthand for rendering a collection of partials

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<%= render @products %>
Rails determines the name of the partial to use by looking at the model name in the collection.

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how to render aheterogeneous collection of cartials

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<%= render [customer1, employee1, customer2, employee2] %>
In this case, Rails will use the customer or employee partials as appropriate for each member of the collection.

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use a custom local variable name within the partial, specify the

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:as option
With this change, you can access an instance of the @products collection as the item local variable within the partial.

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How to pass it variables to the partial which are only defined in the render call

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:locals => {:title => "Products Page"}

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Rails also makes a .... variable available within a partial called by the collection

tell you how many times the partial has been rendered

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counter
For example, if you’re rendering @products, within the partial you can refer to product_counter

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how to specify a second partial to be rendered between instances of the main partial

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<%= render @products, :spacer_template => "product_ruler" %>

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howt o override sections of the main layout (application.html) in layout/news

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app layout <style type="text/css"><%= yield :stylesheets %></style>

layouts/news

<% content_for :stylesheets do %> #top_menu {display: none}
<% end %>

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routing determines which....... to use for a request then

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controller

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Once your controller receives a request via routing it is responsible for ......

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making sense of the request and producing the appropriate output.

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what happens once the routing determines which controller and action to run

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Rails creates an instance of that controller and runs the method with the same name as the action.

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what view will be rendered here and what does this show:
def new
end

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Rails will by default render the new.html.erb view unless the action says otherwise

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regular controllers inherit from

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ApplicationController

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ApplicationController inherits from

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ActionController::Base,

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Only .... controller methods are callable as actions

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public -> thus lower the visibility of methods not intended to be actions (like filters) by putting under private

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What are the two kinds of parameters possible in a web application.

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1 query string parameters
2 POST data

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what is query string parameters

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parameters that are sent as part of the URL, called query string parameters. The query string is everything after “?” in the URL.

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what is POST data

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comes from an HTML form which has been filled in by the user. It’s called POST data because it can only be sent as part of an HTTP POST request.

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Does Rails make any distinction between query string parameters and POST parameters?

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no - both are available in the params hash in your controller:

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how does this get translated into params in a controller:

/clients?status=activated

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params[:status] = "activated"

thus use logic like
if params[:status] == "activated"

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index is a HTTP GET request thus it would use what kind of params

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query string params - e.g. /clients?status=activated

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what is the url submitted when there is a boatload of POST data?

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"/clients", and the data is sent as part of the request body, thus hidden (unlike query params)

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how to send an array of values to the controller

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append an empty pair of square brackets “[]” to the key name:

GET /clients?ids[]=1&ids[]=2&ids[]=3

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how is this encoded irl

GET /clients?ids[]=1&ids[]=2&ids[]=3

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“/clients?ids%5b%5d=1&ids%5b%5d=2&ids%5b%5d=3” as “[” and “]” are not allowed in URLs. Most

don't worry though - rails does this automatically

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parameter values are always .....

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strings;

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Does Rails make any attempt to guess or cast the type of params?

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No - you must do this yourself

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what is params[:ids] here?
ids[]=1&ids[]=2&ids[]=3

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The value of params[:ids] will now be ["1", "2", "3"]

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how do you send a hash of params?

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include the key name inside the brackets:

<input type="text" name="client[name]" value="Acme" />
<input type="text" name="client[phone]" value="12345" />

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<input type="text" name="client[name]" value="Acme" /> <input type="text" name="client[phone]" value="12345" />

what is params[:client]

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, the value of params[:client] will be {"name" => “Acme”, “phone” => “12345”}

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what is the value of params[:client] here?
<input type="text" name="client[address][postcode]" value="12345" />

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{ “address” => {"postcode" => “12345”}}
see how a hash is nested

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what will the params hash always contain?

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the :controller and :action keys

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is the best way to access the controller / action name through the the :controller and :action params keys?

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no use the methods controller_name and action_name instead

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are any other params defined by the routing available - give an example

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yes - e.g. params[:id] might be available

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how to add a route which captures the :status paramater or a url

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map.connect "/clients/:status", :controller => "clients", :action => "index"

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Given:
map.connect "/clients/:status", :controller => "clients", :action => "index"

when a user opens the URL /clients/active, params[:status] will be set to

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“active”

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what is the consequence of this route (look at :foo)

map.connect "/clients/:status", :controller => "clients", :action => "index", :foo => "bar"

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params[:foo] will also be set to “bar” just like it was passed in the query string.

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how to set global default parameters that will be used when generating URLs

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def default_url_options(options) {:locale => I18n.locale}
end

used in controllers (individual or ApplicationController)

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what are sessions used for

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store small amounts of data that will be persisted between requests.

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The session is only available in the ... and ...

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controller and the view

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where does this session storage mechanism store it's data?

CookieStore

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Stores everything on the client.

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where does this session storage mechanism store it's data?

DRbStore

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Stores the data on a DRb server.

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where does this session storage mechanism store it's data?

DRbStore

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Stores the data in a memcache.

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where does this session storage mechanism store it's data?

ActiveRecordStore

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Stores the session data in a database using Active Record.

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Does Rails allow you to pass the session ID in the URL

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No - this is too insecure.

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All session stores use a ... to store a unique ID for each session

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cookie (since passing session id in url is too insecure)

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For 3/4 session stores the ID cookie is used to ...

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look up the session data on the server, e.g. in a database table.

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What is the one exception to looking up session data on the server

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The CookieStore – which stores all session data in the cookie itself (the ID is still available to you if you need it)

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What is the default and recommended session store

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the CookieStore

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2 advantages of CookieStore

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very lightweight and it requires zero setup in a new application in order to use the session.

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cookie data is .... signed to make it tamper-proof

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cryptographically

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cryptographically signed means?

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not encrypted, so anyone with access to it can read its contents but not edit it (Rails will not accept it if it has been edited).

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CookieStore can store around ... of data

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4kb

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How to change session storage mechanism

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config/initializers/session_store.rb

# ActionController::Base.session_store = :active_record_store

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What is your your secret key for?

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verifying cookie session data integrity.

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why should secret be at least 30 characters all random?

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you'll be exposed to dictionary attacks.

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why stake care when changing the secret when using the CookieStore ?

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It will invalidate all existing sessions.

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How are session values stored

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Session values are stored using key/value pairs like a hash:

User.find(session[:current_user_id])

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Do you ever need to disable sessions to speed up an app?

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no. Sessions are lazily loaded. If you don’t access sessions in your action’s code, they will not be loaded.

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How to store something in the session?

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assign it to the key like a hash:

session[:current_user_id] = user.id

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How to remove something from the session?

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assign that key to be nil:
session[:current_user_id] = nil

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Why is the flash a special part of the session which is cleared with each request

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cleared with each request.
his means that values stored there will only be available in the next request, which is useful for storing error messages etc.

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Where is it conventional to display eventual errors or notices from the flash?

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Application layout

<% if flash[:notice] %>
<p class="notice"><%= flash[:notice] %></p>
<% end %>

<% if flash[:error] %>
<p class="error">
<%= flash[:error] %></p>
<% end %>

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what are the two conventional types of flash?

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flash[:error]
flash[:notice]

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How do you get a flash value to be carried over to another request,

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use the keep method:

# Let's say this action corresponds to root_url, but you want # all requests here to be redirected to UsersController#index. # If an action sets the flash and redirects here, the values # would normally be lost when another redirect happens, but you # can use 'keep' to make it persist for another request.

def index
# Will persist all flash values.
flash.keep

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How to keep only some kind of flash value.

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# flash.keep(:notice)

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How to access flash values in the same request (e.g. if the create action fails to save a resource and you render the new template directly, that’s not going to result in a new request)

Back 142

if @client.save
# ...
else
flash.now[:error] = "Could not save client"
render :action => "new"

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namespace :backups do

desc "backup db from heroku and send to S3"
task :backup => :environment do

how to run this rake task

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rake backups:backup

namespace:task is the format

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task :the_task do
p "one"
end

task :the_task do
p "two"
end

rake the_task shows what?
what does this show?

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Rake::Task[:the_task].invoke
# >> "one"
# >> "two"

rake tasks append behaviour!

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How to Auto-fill the commenter's name if it has been stored in a cookie ?

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@comment = Comment.new(:name => cookies[:commenter_name])

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How to remember the commenter's name in a cookie?

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cookies[:commenter_name] = @comment.name

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How to delete cookie for the commenter's name cookie, if any

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cookies.delete(:commenter_name)

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What is the difference between clearing session and cookie values?

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session values are set to nil
coookies use cookies.delete(:key)

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What are filters?

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methods that are run before, after or “around” a controller action.

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How to run a filter on every controller in your application.

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set a filter on ApplicationController

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how to define a before filter

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class ApplicationController < ActionController::Base

before_filter :require_login

private
def require_login
......

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What does this do:
!!current_user

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converts something to true or false (instead of giving a user object or nil here)

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Give an example of a basic reqire_login filter which halts the request cycle if not logged in

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def require_login
unless logged_in?
redirect_to new_login_url
# halts request cycle
end
end

#logged in can be defined further in the contorller private methods

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If a before filter renders or redirects, the action will .....

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not run

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If there are additional filters scheduled to run after a filter which renderes or redirects they are ...

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also cancelled.

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How to prevent a filter from running before particular actions (assuming the filter is in application controller)

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class LoginsController < ApplicationController

skip_before_filter :require_login, :only => [:new, :create]

#note how the code is within the logins controller (even though the filter is in original backup)

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what filter runs once a controller action has already run

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after_filter

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what filter is run both before and after a controller filter

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around_filter

around_filter :catch_exceptions

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Two other ways to use controller fiters

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1. Use a class
before_filter LoginFilter

2 Use a block
before_filter do |controller| redirect_to new_login_url unless controller.send(:logged_in?)
end
#send is used here since logged_in? is a private method

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When to use a class for a filter?

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Cases that are more complex and can not be implemented in a readable and reusable way using the two other methods.

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What does a filter class look like?

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class LoginFilter
def self.filter(controller)
unless controller.send(:logged_in?) controller.flash[:error] = "You must be logged in"
controller.redirect_to controller.new_login_url
end
end

#note the use of the controller object

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What do verifications do?

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make sure certain criteria are met in order for a controller or action to run.

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Controller Verification can specify that a certain key (or several keys in the form of an array) is present in the ...
hashes

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1 params hash
2 session hash
3 flash hashe

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Controller Verification can also specify that a certain .... method was used

Back 164

HTTP METHOD

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What default action does controlelr verification take when its criteria are not met?

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render a 400 Bad Request response, but you can customize this by specifying a redirect URL or rendering something else

# in a controller
verify :params => [:username, :password],
:render => {:action => "new"}

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How to add a flash to a verification

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verify :params => [:username, :password],
:add_flash => { :error => "Username and password required to log in" }

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verifications are by default used for .... action in the contoller

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verifications are used for every action

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how to specify a verification should only run for certain actions

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verify ..., :only => :create

#except also works too... like filters

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how to view the history of a file in git

Back 169

gitk service_provider.rb

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how to troubleshoot errors with migrating down?

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look for spelling inconsistencies between up and down methods

check for premptive table downs (on migration files despite previous ones requiring)

go into sql and desc tables

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First step to avoid Cross-site request forgery

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make sure all “destructive” actions (create, update and destroy) can only be accessed with non-GET requests. If you’re following RESTful conventions you’re already doing this.

Front 172

How to avoid Cross-site request forgery given that some attacks can come as a non-GET request?

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request forgery protection

add a non-guessable token which is only known to your server to each request. This way, if a request comes in without the proper token, it will be denied access.

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How to active cross site request forgery protect

Back 173

Rails adds this token to every form that’s generated using the form helpers, so most of the time you don’t have to worry about it unless you’re writing a form manually

Front 174

Given that rails auto adds forgery protection to forms, how do these forms look?

Back 174

<form action="/users/1" method="post"> <
input type="hidden" value="67250ab105eb5ad10851c00a5621854a23af5489" name="authenticity_token"/>
<!-- fields -->
</form>

Front 175

what method is used to manually protect from forgery?

Back 175

form_authenticity_token

Front 176

what two speciall accessor methods does every controller have?

Back 176

methods pointing to the request and the response objects associated with the request cycle that is currently in execution.

Front 177

request method contains an instance of ....

Back 177

AbstractRequest

Front 178

response method contains

Back 178

response object representing what is going to be sent back to the client.

Front 179

how to filter out sensitive information from the log.

Back 179

filter_parameter_logging method

Front 180

How to use filter_parameter_logging method

Back 180

class ApplicationController < ActionController::Base filter_parameter_logging :password end

Front 181

How does the filter_parameter_logging method work?

Back 181

It works by replacing certain values in the params hash with “[FILTERED]” as they are written to the log

Front 182

f the user follows a link to a resource that no longer exists in the database, Active Record will throw the ...

Back 182

ActiveRecord::RecordNotFound exception.

Front 183

“404 Not Found” is shown if ... or ...

Back 183

1 if there was a routing error or
2 a record could not be found.

Front 184

By default a production application will render either a ... or a ... error message

Back 184

404 or a 500

Front 185

How to rescue from certain errors in a controller

Back 185

rescue_from ActiveRecord::RecordNotFound, :with => :record_not_found

private
def record_not_found
render :text => "404 Not Found", :status => 404
end

Front 186

If you want to be hardcore about exceptions what could you do?

Back 186

you could create custom exception classes that will be thrown

Front 187

How to raise a custom exception

Back 187

Have a filter with a custom method in a controller

that custome method should raise the new exception e.g.

def check_authorization
raise User::NotAuthorized unless current_user.admin?
end

Front 188

Why is It is not recommended that you stream static files through Rails?

Back 188

you can instead keep them in a public folder on your web server. It is much more efficient to let the user download the file directly using Apache or another web server, keeping the request from unnecessarily going through the whole Rails stack

Front 189

What is the (unrecommended) way to send files that already exist on disk?

Back 189

send_file("#{Rails.root}/files/clients/#{client.id}.pdf", :filename => "#{client.name}.pdf", :type => "application/pdf")

#done within a method in the controller e.g. def download_pdf

Front 190

Why is send_data not restful?

Back 190

having separate actions for file downloads is usually not necessary. In REST terminology, the PDF file from the example above can be considered just another representation of the client resource

Front 191

What is the sleek way of doing “RESTful downloads”?

Back 191

def show
@client = Client.find(params[:id]) respond_to do |format|
format.html
format.pdf { render :pdf => generate_pdf(@client) }
end

#remember to add the PDF MIME TYPE

Front 192

Where are mime types kept in rails?

Back 192

config/initializers/mime_types.rb:

Front 193

How to add a mime type in config/initializers/mime_types.rb:

Back 193

Mime::Type.register "application/pdf", :pdf

Front 194

Are Configuration files (such as initializzers) not reloaded on each request?

Back 194

NO - have to restart the server in order for their changes to take effect.

Front 195

When something fishy is going wrong using a gem method what should you try?

Back 195

see if the gem has been updated - it's possible an old version may be play

Front 196

How to get the url requested?

Back 196

Request.url

Front 197

How to get the method used for the request?

Back 197

Request.method

Front 198

How to get the The query string part of the URL, i.e., everything after “?”.

Back 198

Request.query_string

Front 199

How to get yhe IP address of the client?

Back 199

Request.remote_ip

Front 200

What three accessors does the request object have that give you access to paramets?

Back 200

query_parameters hash
request_parameters hash
path_parameters hash

Front 201

Some of these accessor methods for the response object also have ....

Back 201

setters, allowing you to change their values.

Front 202

How to access the string of data being sent back to the client. This is most often HTML?

Back 202

Response.body

Front 203

How to access the HTTP status code for the response, like 200 for a successful request or 404 for file not found.

Back 203

Response.status

Front 204

How to access the URL the client is being redirected to, if any.

Back 204

Response.location

Front 205

How to access the content type of the response.

Back 205

Response.content_type

Front 206

How to use Rail's built-in authentication?

Back 206

authenticate_or_request_with_http_basic.

[not recommended as there it passes password unencrypted over http (though not https)

Front 207

What would go inside a method which authenticated using authenticate_or_request_with_http_basic ?

Back 207

authenticate_or_request_with_http_basic do
|username, password|

username == USERNAME && Digest::SHA1.hexdigest(password) == PASSWORD

end

Front 208

If you have a controller with filters and private methods you'd like to apply to other controllers how do you inherit?

Back 208

create namespaced controllers that inherit from AdminController

Front 209

What is superior to authenticate_or_request_with_http_basic.

Back 209

authenticate_or_request_with_http_digest

password is encrypted

Front 210

give an example of authentication using
authenticate_or_request_with_http_digest

Back 210

authenticate_or_request_with_http_digest do
|username|
USERS[username]

#top of controller
USERS = { "lifo" => "world" }
end

Front 211

When a form_tag is called on it's own what action and HTTP method is used?
<% form_tag do %>
#contents
<% end %>

Back 211

action -> current page
method -> post

Front 212

what HTTP mehod should you use for search forms?

Back 212

GET -> since users need to be able to bookmark specific searches and get back

Front 213

how to specify a get method and the search_path url in a form?

Back 213

<%= form_tag(search_path, :method => "get" do %>
label_tag
text_field_tag
submit_tag

Front 214

what shortcut can you use for specifying methods to use in a form?

Back 214

named routes - e.g. form_tag(search_path)

Front 215

for every form input an ...... is generated from it's name
and this is useful for .......

Back 215

Every form input has an ID attribute generated from its name - useful for CSS/JS

Front 216

what's wrong with this:

form_tag(:controller => "people", :action => "search", :method => "get", :class => "nifty_form")

compared to:
form_tag({:controller => "people", :action => "search"}, :method => "get", :class => "nifty_form")

Back 216

Here you wanted to pass two hashes, but the Ruby interpreter sees only one hash, so Rails will construct a URL with extraneous parameters
# => <form action="/people/search?method=get&class=nifty_form" method="post">

Front 217

if a form helper has unexpected output what should you do?

Back 217

make sure that you have delimited the hash parameters properly.

Front 218

if the form contains
<%= text_field_tag(:query) %>

then the controller code can access the input with

Back 218

params[:query]

Front 219

These basic helpers, with names ending in _tag such as text_field_tag, check_box_tag take as a first parameter...

Back 219

the name of the input (which is assigned as the key in the params)

Front 220

how to specify a text_field_tag for surname

Back 220

<%= text_field_tag(:surname) %>

Front 221

How do you specify which value a check box tag will submit when a checkbox is ticked?

Back 221

the second param
<%= check_box_tag(:pet_cat, "I own a cat") %>

#if ticked i own a cat is submitted

Front 222

How to access this check boxes details in the controller?
<%= check_box_tag(:pet_cat, "I own a cat") %>

Back 222

params[:pet_dog]

Front 223

Difference between checkboxes and radio buttons?

Back 223

Radio boxes are sets of options which are mutually exclusive, where users can pick multiple checkboxes

Front 224

Why should you always use labels for each checkbox and radio button?

Back 224

They associate text with a specific option and provide a larger clickable region.

Front 225

How do you specify that two radio buttons be mutually exclusive? ie choose one of the other

Back 225

Give both the same name (first param)
<%= radio_button_tag(:age, "adult") %>
<%= radio_button_tag(:age, "child") %>

Front 226

How to have a label for a radio_button differ from the value passed?

Back 226

<%= radio_button_tag(:age, "child") %> <%= label_tag(:age_child, "I am younger than 21") %>
#I am younger than displayed
#child passed

Front 227

form helper for passwords

Back 227

password_field_tag(:password)

Front 228

how to pass hidden options via a form

Back 228

<%= hidden_field_tag(:parent_id, "5") %>

Front 229

Values inside hidden fields can be changed with ....

Back 229

JavaScript.

Front 230

how to stop passwords showing in logs?

Back 230

filter_parameter_logging(:password)
#assumes password input field
#place this in applicationcontroller

Front 231

Can the _tag helpers be used for created and editing a model?

Back 231

Yes - but overly verbose - one big problem is that the defaults are not filled in

Front 232

Model objects helper first arg?

Back 232

An instance variable (usually name of model)
E.g. <%= text_field(:person, :name) %
>
#assumes the controller has a @person set

Front 233

Model objects helper second arg?

Back 233

<%= text_field(:person, :name) %

the method name (usually attribute) to call on object

Front 234

what html does this translate to?
<%= text_field(:person, :name) %>

#assuming current name=Henry

Back 234

<input id="person_name" name="person[name]" type="text" value="Henry"/>

Front 235

where in the params is the value stored

<%= text_field(:person, :name) %>

Back 235

params[:person][:name]

Front 236

<%= text_field(:person, :name) %>

If a person model has no name attribute in the db how will this work?

Back 236

Just saving any name= method

Front 237

Why bind a form to an object?

Back 237

Efficiency. If Person (model) has many attributes to edit then we would be repeating the name of the edited object many times

Front 238

How to bind a form to article model and create a text field?

Back 238

<%= form_for :article, @article, :url => { :action => "create" } do |f| %>

<%= f.text_field :title %>

Front 239

The form_for method yields what?

Back 239

a form builder object
e.g. f

form_for :article, @article do |f|
#f can have input fields called off it

Front 240

form_for :article, @article

What is the difference between the first and second param

Back 240

1st parm is the model name
2nd param is the actual object being editted

Front 241

how to change the url form_for passes to?

Back 241

form_for :article, @article, :url => { :action => "create" }

#turn to :<form action="/articles/create"

Front 242

<%= form_for :article, @article do |f| %>
<%= f. etc. %>

how to access the inputs

Back 242

all the inputs have names of the form article[attribute_name]. Accordingly, in the action params[:article] will be a hash with keys :title and :body.

Front 243

Once you've bound an object to a form using form for, what can you omit from the helper fields?

Back 243

The object name. Code like this suffices:
<%= f.text_field :title %>

Front 244

how do you edit additional model objects with the same form

Back 244

fields_for form builder nested with form_for

<%= form_for :person, @person do |person_form| %>
<%= person_form.text_field :name %>
<%= fields_for @person.contact_detail do |contact_details_form| %>

Front 245

When dealing with RESTful resources (i.e. you declared map.resources in the routes), calls to form_for can use what shortcut?

Back 245

form_for(@article)
#uses record identification

instead of
#new
form_for(:article, @article, :url => articles_path)
#edit
form_for(:article, @article, :url => article_path(@article), :html => { :method => "put" })

Front 246

how is short-style form_for invocation is the same, regardless of the record being new or existing

Back 246

it figures out if the record is new by asking record.new_record?

Front 247

Rails will also automatically set the class and id of the form appropriately: a form creating an article would have id and class .....

Back 247

new_article.

Front 248

Rails will also automatically set the class and id of the form appropriately: If you were editing the article with id 23, the class would be set to ...... and the id to .....

Back 248

edit_article (class)
edit_article_23 (id)

Front 249

How to create a form that submits to the articles controller inside the admin namespace?

Back 249

form_for [:admin, @article]
#udpate - subbmitting to admin_article_path(@article)

Front 250

How to create a form that submits to the article controller inside the managment namespace, itself inside the admin namespace?

#i.e. deeply nested

Back 250

form_for [:admin, :management, @article]

Front 251

most browsers don’t support methods other than “GET” and “POST” when it comes to submitting forms. How does Rails get around this?

Back 251

Rails works around this issue by emulating other methods over POST with a hidden input named "_method", which is set to reflect the desired method:

<input name="_method" type="hidden" value="put" />

Front 252

how to specify that a form should put rather than post?

Back 252

form_tag(search_path, :method => "put")

Front 253

how to make select boxes (form not bound to a model)?

Back 253

<%= select_tag(:city_id, options_for_select([['Lisbon', 1], ['Madrid', 2], ...])) %>

Front 254

The first argument to options_for_select is

Back 254

a nested array where each element has two elements: option text (city name) and option value (city id).

options_for_select([['Lisbon', 1], ['Madrid', 2], ...])

Front 255

how does options_for_select allow you to pre-select an option by passing its value.

Back 255

pass it in as the second param (once the first param, the array, is closed)

<%= options_for_select([['Lisbon', 1], ['Madrid', 2], ...], 2) %>

#adds the selected attribute to whatever has the value of 2 in the form

Front 256

how to make select boxes (form bound to a model)

Back 256

#form_for :person

<%= f.select( :city_id, [['Lisbon', 1], ['Madrid', 2], ...]) %>

#don’t have to worry about pre-selecting the correct city if the user already has one — Rails will do this for you by reading from the @person.city_id attribute.

Front 257

If you are using select (or similar helpers such as collection_select, select_tag) to set a belongs_to association you must pass the name of the .........

Back 257

foreign key (in the example above city_id), not the name of association itself.

%= select(:person, :city_id, ...

Front 258

ActiveRecord::AssociationTypeMismatch: City(#17815740) expected, got String(#1138750) means

Back 258

you prob passed name of an association to a form, rather than the foreign key it expected

Front 259

<%= options_from_collection_for_select(City.all, :id, :name) %>

explain

Back 259

1st param -> bunch of objects (City.all)
2nd param - value for option (:id)
3rd param - text displayed (:name)

As the name implies, this only generates option tags. T

Front 260

When working with model objects collection_select combines .....

Back 260

select_tag with options_from_collection_for_select.

<%= collection_select(:person, :city_id, City.all, :id, :name) %>

Front 261

To leverage time zone support in Rails, you have to ask your users what time zone they are in. Easiest way to do this?

Back 261

<%= time_zone_select(:person, :time_zone) %>

Front 262

Dates and times are not representable by a .... input element

Back 262

Single. Instead you have several, one for each component (year, month, day etc.) and so there is no single value in your params hash with your date or time.

Front 263

How to specify a barebones date / time helper (_tag suffix equivalent)

Back 263

select_date, select_time and select_datetime

#select comes before with barebones
select_*

Front 264

How to specify a model object date / time helper?

Back 264

date_select, time_select and datetime_select

#select comes after with object

Front 265

What is the first argument of the select_* family of date / time helpers

Back 265

an instance of Date, Time or DateTime that is used as the currently selected value.
<%= select_date Date.today %>

Front 266

What happens if you omit the first argument of the select_* family of date . time helpers (first param is current selected value)...

Back 266

It use the current date

Front 267

<%= select_date Date.today, :prefix => :start_date %> results in what params

Back 267

params[:start_date][year]
params[:start_date][month]
params[:start_date][day]

Front 268

How do you turn the output of a select_date helper into an actual Date or Time object?
#necessary since the three params it produces are just strings

Back 268

extract these values and pass them to the appropriate constructor, for example

Date.civil(params[:start_date][:year].to_i, params[:start_date][:month].to_i, params[:start_date][:day].to_i)

Front 269

How to create an object bound date/time select for the birth_date attribute of a person model

Back 269

<%= date_select :person, :birth_date %>

Front 270

How is this represented in HTML and why? <%= date_select :person, :birth_date %>

Back 270

<select id="person_birth_date_1i" name="person[birth_date(1i)]"> ... </select>
<select id="person_birth_date_2i" name="person[birth_date(2i)]"> ... </select>
etc.
#the 1i,2i,3i (not shown) are used by AR to construct the birth_date attribute

Front 271

How is this represented in the params <%= date_select :person, :birth_date %>

Back 271

{:person => {'birth_date(1i)' => '2008', 'birth_date(2i)' => '11', 'birth_date(3i)' => '22'}}

Front 272

By default Rails date time helpers generate year options how many years each side of the current year?

Back 272

5 years
To overide pass a :start_year and an :end_year option

Front 273

As a rule of thumb you should be using date_select when .... and select_date i...

Back 273

date select when working with model objects
select_date in other cases, such as a search form which filters results by date

Front 274

How to specify a single date component such as a year or a month.

Back 274

select_year, select_month, select_day, select_hour, select_minute, select_second

Front 275

select_year, select_month, select_day, etc. generate an input field named after....

Back 275

input field named after the time component (for example “year” for select_year, “month” for select_month etc.) although this can be overriden with the :field_name option.

Front 276

How to set the selected value of select_year, select_month, select_day, etc.

Back 276

either be an instance of a Date, Time or DateTime,
<%= select_year(2009) %> <%= select_year(Time.now) %>

Front 277

<%= select_year(2009) %> is a instance of the singular date helpers. How do you access these params in the controller

Back 277

the value chosen by the user can be retrieved by params[:date][:year].

Front 278

What must you do to be able to upload files to a form?

Back 278

Set the form's encoding to multippart/form-data
<% form_for @person, :html => {:multipart => true} do |f| %>

Front 279

What is the difference between setting multi-part to true for form_tags and form_forms?

Back 279

<% form_tag({:action => :upload}, :multipart => true) do %>
#passed in the second options hash (which is the html one)

<% form_for @person, :html => {:multipart => true} do |f| %>
#passed as a html option

Front 280

What form helper is used to upload files for form_fors

Back 280

<%= f.file_field :picture %>

Front 281

What form helper is used to upload files for form_tags

Back 281

<%= file_field_tag 'picture' %>

Front 282

The file object in the params hash is an instance of a ....

Back 282

subclass of IO

Front 283

How to access the file just uploaded in a Rails form in the params?

Back 283

params[:person][:picture]
# good practice is to assign this to a var
e.g pic = p

Front 284

what attribute do uploaded file objects have

Back 284

original_filename
thus
uploaded_io = params[:person][:picture]
uploaded_io.original_filename

Front 285

making an asynchronous file upload form is not as simple as replacing form_for with remote_form_for. Why? Workaround?

Back 285

With an Ajax form the serialization is done by JavaScript running inside the browser and since JavaScript cannot read files from your hard drive the file cannot be uploaded. The most common workaround is to use an invisible iframe that serves as the target for the form submission.

Front 286

form_for and fields_for are subclasses of?

Back 286

FormBuilder

Front 287

How to build custom Form builders?

Back 287

class LabellingFormBuilder < ActionView::Helpers::FormBuilder

def text_field(attribute, options={}) label(attribute) + super
end
end

Front 288

How to use a custom form builder (LabellingFormBuilder in this case)

Back 288

<% form_for @person, :builder => LabellingFormBuilder do |f| %> <%= f.text_field :first_name %> <% end %>

#assumes you've elsewhere defined t

Front 289

HTML forms don’t know about any sort of structured data, all they generate is ...

Back 289

name-value pairs - where both are just plain strings

Front 290

How to try out rails paramater parser in the console?

Back 290

ActionController::UrlEncodedPairParser.parse_query_parameters “name=fred&phone=0123456789”

Front 291

For a params hash of {'person' => {'name' => 'Henry'}} what will the input form look like?

Back 291

<input id="person_name" name="person[name]" type="text" value="Henry"/>

#note the id outerkey_innerkey and name = outerkey[innerkey] and value = value

Front 292

How will a tri nested params hash look?
{'person' => {'address' => {'city' => 'New York'}}}

Back 292

<input id="person_address_city" name="person[address][city]" type="text" value="New York"/>

#look at how its outermostkey_middlekey_innerkey in id and out[mid][inner] in name

Front 293

How to accumulate params in an array?

Back 293

The parameter name must contain an empty set of square brackets []
<input name="person[phone_number][]" type="text"/> <input name="person[phone_number][]" type="text"/>
#two phone numbers

Front 294

How to make params[:person][:phone_number] an array instead of a single item?

Back 294

<input name="person[phone_number][]" type="text"/>

<input name="person[phone_number][]" type="text"/>

Front 295

How to make params[:addresses] an array of hashes each with keys line1, line2 and city?

Back 295

#put the square brackets after the item which is supposed to contain an arrary - then deeper nested items will dictate the hash structure of said array

<input name="addresses[][line1]" type="text"/>
<input name="addresses[][line2]" type="text"/>
<input name="addresses[][city]" type="text"/>

Front 296

What restriction is placed on arrays in params?

Back 296

only one level of “arrayness” is allowed -i.e. no deep nesting

Front 297

Whats a good way to represent a set of models in params using hashes?

Back 297

a hash of model objects keyed by their id

Front 298

check_box helper doesn't play well with arays since the duplicate input names created by the hidden input submitted when unchecked confuses Rails (doesn't know whether array or not). What to use instead?

Back 298

check_box_tag

Front 299

What form action html is created by this edit form (assuming person has id of 1)?
<% form_for @person do |person_form| %>

Back 299

#/people/1 - a url
# and method =post

<form action="/people/1" class="edit_person" id="edit_person_1" method="post">

Front 300

What class does this edit form (assuming person has id of 1)?
<% form_for @person do |person_form| %> create?

Back 300

#edit_person

<form action="/people/1" class="edit_person" id="edit_person_1" method="post">

Front 301

What id does this edit form (assuming person has id of 1)?
<% form_for @person do |person_form| %> create?

Back 301

#edit_person_1
# items id is used

<form action="/people/1" class="edit_person" id="edit_person_1" method="post">

Front 302

. If you pass an Active Record object as we did then Rails will call to_param on it, which by default returns the ......

Back 302

database id.

#thus @person.to_param = 23

Front 303

What does the index option for form_for and fields_for do?

<% person_form.fields_for address, :index => address

Back 303

it inserts that index between the preceding and following param

person[address][ *index_item* ]
person[address][4] actually (since the index is passed an AR object)

Front 304

How to get params like this?
{'person' => {'name' => 'Bob', 'address' => {'23' => {'city' => 'Paris'}, '45' => {'city' => 'London'}}}}

Back 304

form_for person
f.name
for address in @person.addresses
#setting the variable
fields_for address :index => address

Front 305

What is the advantage of params like this?
{'person' => {'name' => 'Bob', 'address' => {'23' => {'city' => 'Paris'}, '45' => {'city' => 'London'}}}

Back 305

#great for locating which AR record to modify

Front 306

How to specify the first part of the input name (person[address] explicity?

Back 306

<% fields_for 'person[address][primary]', address do |address_form| %>

Front 307

How to generate a generator?

Back 307

rails g generator NAME

Front 308

When you generate a generator (within a rails app) where do the files go?

Back 308

lib/generator-name/

Front 309

Every ...... in the x_generator.rb file will be run when that generator is called in future.

Back 309

public method

Front 310

If you want to create a method in a generator which is not automatically run when the generator is call ed make is a .....

Back 310

private method

Front 311

By default a generated generator inherits from
....

Back 311

Rails::Generators::NamedBase

Front 312

Rails::Generators::NamedBase inheritance means that ....

Back 312

a name must be supplied when calling the generator

Front 313

If you want the supply of a name to be optional when calling a generator change the inheritance to inherit from .....

Back 313

Rails::Generators::Base

Front 314

What method is used to define arguments for your generator? (i.e. extra bits that can be entered at command line and assigned as variables within the generator?

Back 314

argument :layout_name, :type => :string

#write this just under the source_path method

Front 315

How to give an argument in a generator a default should nothing be provided at command line?

Back 315

argument :layout_name, :type => :string

Front 316

when you run rails g layout --help and you see an argument in square brackets (e.g. [LAYOUT_NAME] what does this mean?

Back 316

that the argument is optional

Front 317

By default where do you put files within a generator which you want to copy over to the application when the generator is run?

Back 317

the template folder

Front 318

How should you name the public methods in your generator?

Back 318

after what they create (e.g. generate_stylesheet) - helps organize code better

Front 319

How to copy the "stylesheet.css" file from the template folder in a generator to your app?

Back 319

copy_file "stylesheet.css", "public/stylesheets/#{layout_name}"

Front 320

copy_files 2nd param is?

Back 320

where you want the copied file to end up in your app - director name and filename

copy_file "stylesheet.css", "public/stylesheets/#{layout_name}.css"

Front 321

Rails only method to turn a CamelCased string into an underscored_one

Back 321

.underscore
#useful for formatting arguments which will be turned into filenames

Front 322

Difference between copy_file and tempalte

Back 322

copy_file does a straight copy of file without modifying it at all - template modifyes the resulting file when the generator runs

Front 323

The template method will execute all the ....

Back 323

erb tags within the .erb file you are templating. Bad since might cause generator to crash with unknown methods

Front 324

How to modify erb template files so that template method doesn't execute all the erb

Back 324

change <% and <%= to <%% and <%%=
#i.e. change the first one so as to escape it

Front 325

Within template files of a generator how do you access methods within the x_generator.rb file

Back 325

<%= method_name %>
#regular unescaped erb here
#can even use private methods

Front 326

How to add a cmd line option to you generator

Back 326

before declaring the public methods call class_option :stylesheet, :type => boolean, :default => true, :desc => "Include Stylesheet File"

Front 327

How to access command line options within a generator?

Back 327

call the option name from the options object

e.g. options.stylesheet if you declared
class_option :stylesheet

Front 328

How to make copying certain fiels within the generator optional?

Back 328

copy file ..... if options.stylesheet?

#where this is a boolean defaulting to true

Front 329

How to remove certain lines from a tempalte depending on command line options?

Back 329

<%- if options.sytlesheet? -%>
dfdsfs
<%- end -%>

Front 330

How to put a generator in a gem so as to share with others?

Back 330

Create a dir in the gem called lib/generators are place you generator inside. Once they include the gem in their application it will be available for them to use

Front 331

How to see all the generators available to your app?

Back 331

rails g

#will show the generators available for different items for different tasks (e.g. shoulda might have model but not scaffold)

Front 332

How to see options with a given generator (e.g. scaffold?

Back 332

rails g scaffold --help

Front 333

Many generator options have ...

Back 333

default values (seen with --help)

Front 334

How to disable a boolean that defaults to try in a generator

e.g. -stylehsheets defaults to true

Back 334

--no in front of option name

rails g scaffold --no-sytlesheets

Front 335

In the output of a generator what does invoke mean?

Back 335

invokes a separate generator - shows that a high level generator delegates work onto other generators - e.g. scaffold invokes acive_record generator

Front 336

How do you have a generator option added everytime you run a generator without typing it every time?

Back 336

application.rb

config.generators do |g|
g.tempalte_engine :haml
end
#put any options you saw in the generator help

Front 337

To use certain generator options you need to ensure the gems are ...

Back 337

added to the Gemfile

Front 338

If your gem doesn't include generators then you should check ...

Back 338

gem "rails3-generators", :group => :development

#this gives you lots of new generators only in dev area so production not clogged up

Front 339

If you see error shoulda [not found] in place of invoke when running a generator what does this mean?

Back 339

Rails could not find a shoulda generator for the high level task (e.g. rails g scaffold)

Front 340

What is a generator fallback?

Back 340

Says that if a generator is not found (e.g. shoulda) it will use someting else

#within the generator block

g.fallbacks[:shoulda] = :test_unit

Front 341

Where to put generator fallbacks ?
Rails::Generators.fallbacks[:shoulda] = :test_unit

Back 341

at the bottom of the application.rb file

Front 342

How to override the tempalte of the generators rails gives you?

Back 342

add files to lib/templates

Front 343

How to find name of the templates you wish to override with your generator!

Back 343

railes/railties/lib/rails/generators/ on rails github

#thus for ...generators/scaffold/erb/index.html.erb you need to create a dir in the lib/templates dir locally called erb/scaffold

Front 344

How to add a description to your custom generator?

Back 344

1. Call the desc method within the generator (just under the class defition and inheritance)

desc "This generator creates an initializer file at config/initializers"

2. Create a USAGE file

Front 345

What method is automatically created when we inherit from Rails::Generators::NamedBase.

Back 345

file_name - set to argument supplied at cmd line

Front 346

How to use the create_file method in a generator

Back 346

#second parm is file contents and is between <<--FILE and FILE

create_file "app/helpers/#{file_name}_helper.rb", <<-FILE

module #{class_name}Helper attr_reader :#{plural_name}, :#{plural_name.singularize}
end

FILE
end

Front 347

What are hooks within generators?

Back 347

Generators do not need to be focused in one specific test framework, it can simply provide a hook and a test framework just needs to implement this hook in order to be compatible.

Front 348

How to use a hook within a generator for test framework?

Back 348

hook_for :test_framework

Front 349

When TestUnit is configured as the test framework and it sees hook_for :test_framework within a class MyHelperGenerator what will it try to invoke?

Back 349

MyHelper::Generators::TestUnitGenerator

#this is undefined - instead it only sees helper

Front 350

How to specify in a generator hook to look for a different generator to invoke

Back 350

# Search for :helper instead of :my_helper hook_for :test_framework, :as => :helper

Front 351

Within a template file how do you get a class to dynamically be input?

Back 351

<%= class_name %>

Front 352

Within a template file how do you get the plural name to dynamically be input?

Back 352

<%= plural_name %>

Front 353

Within a template file how do you get the singular name to dynamically be input?

Back 353

<%= plural_name.singularize %>

Front 354

What do hooks do in generators?

Back 354

allow one generator to call another

Front 355

What order do arguments and options to a generator come in when parsing params?

Back 355

first params are arguments, last ones are options

Front 356

The order arguments are decalred in a generator is ....

Back 356

the order they will be accepted on the command line

Front 357

how to specify a generator argument in a number

Back 357

:type => :numeric

Front 358

Once an argument to a generator is declared optional, all remaining arguments....

Back 358

must be optional

Front 359

Once an array argument is declared (:type => :array) everything after it is

Back 359

parsed into the array

Front 360

How to set an option when calling a generator?

Back 360

--name-of-option

Front 361

Generators inherit all the methods of what useful file manipulation suite?

Back 361

Thor::Actions

Front 362

How to add a single line of text to the end of a file with a generator?

Back 362

append_file 'config/environments/test.rb', 'config.gem "rspec"

Front 363

How to add multiple lines of text to the end of a file with a generator?

Back 363

append_file 'config/environments/test.rb' do
'config.gem "rspec"'
end

Front 364

How to add a single line of text to the TOP of a file with a generator?

Back 364

prepend_file 'config/environments/test.rb', 'config.gem "rspec"'

Front 365

How to run a regular expression replacement on a file in a generator?

Back 365

gsub_file 'app/controllers/application_controller.rb', /app_name/, 'hermestech'

Front 366

What is the 2nd param for gsub_file?

Back 366

the flag - regex or string to be replaced

Front 367

What is the 3rd param for gsub_file

Back 367

the replacement text (can be given as a block too)

Front 368

How to download the content at the given address and places it at the given relative destination?

Back 368

get "http://gist.github.com/103208", "doc/README"

Front 369

How to create an empty directory in a generator?

Back 369

empty_directory "doc"

Front 370

How to load an external file and execute it in a generator?

Back 370

apply "http://gist.github.com/103208"
apply "recipes/jquery.rb"

Front 371

How to execute a linux command inside a generator?

Back 371

run('ln -s ~/edge rails')

Front 372

How to execute a linux command within a certain folder of the new app inside a generator?

Back 372

inside('vendor') do
run('ln -s ~/edge rails')
end

Front 373

How to remove a file from a rails app in a generator

Back 373

remove_file 'app/controllers/application_controller.rb'

Front 374

How to add text after a certain point in an existing file?

Back 374

inject_into_file "config/environment.rb", "config.gem :thor", :after => "Rails::Initializer.run do |config|\n"

Front 375

How to add text right after the class definition of an existing class?

Back 375

inject_into_class "app/controllers/application_controller.rb", " filter_parameter :password\n"

Front 376

How to run git commands it a rails generator?

Back 376

git :command => "arg"

git :init
git :add => '.'
git :commit => "-a -m 'Initial commit'"

Front 377

How to add routes in a rails generator?

Back 377

route "map.root :controller => 'pages', :action => 'index'"

Front 378

How to run a generator from a rails generator

Back 378

generate :controller, "pages index"

#first param is generator type, second is args

Front 379

How to add a gem from a Rails generator?

Back 379

gem 'inherited_resources', :version => '1.0.3'

Front 380

How to run a rakefile from a Rails generator?

Back 380

rake "db:migrate"

Front 381

how to install a plugin from a generator?

Back 381

plugin "dry_scaffold", :git => "git://github.com/stasl/dry_scaffold.git"

Front 382

Find the client with primary key (id) 10.

Back 382

client = Client.find(10)

Front 383

sql equivalent of client = Client.find(10)

Back 383

SELECT * FROM clients WHERE (clients.id = 10)

Front 384

ActiveRecord::RecordNotFound is raised when

Back 384

Model.find(primary_key) doesnt find any records

Front 385

How to find the first record matched by the supplied options

Back 385

client = Client.first

Front 386

sql equivalent of client = Client.first

Back 386

SELECT * FROM clients LIMIT 1

Front 387

Does client.first raise an exception if no matches are found (like find(1) would)?

Back 387

no - nil is returned if no matches are found

Front 388

finds the last record matched by the supplied options

Back 388

client = Client.last

Front 389

sql equivalent of client = Client.last

Back 389

SELECT * FROM clients ORDER BY clients.id DESC LIMIT 1

Front 390

Find the client with primary key (id) 1 and 10 in one go

Back 390

client = Client.find(1, 10)

Front 391

sql equivalent of client = Client.find(1, 10)

Back 391

SELECT * FROM clients WHERE (clients.id IN (1,10))

Front 392

When the user table has 1000s of rows what is wrong with this code?

User.each do |user| NewsLetter.weekly_deliver(user)
end

Back 392

INefficient

This is because User.each makes Active Record fetch the entire table, build a model object per row, and keep the entire array in the memory. Sometimes that is just too many objects and demands too much memory.

Front 393

What does find_each do?

Back 393

find_each fetches rows in batches of 1000 and yields them one by one

#much more efficient when a table has thousands of rows

Front 394

how to configure the batch size of find_each?

Back 394

option :batch_size => 2000

User.find_each(:batch_size => 5000) do |user| NewsLetter.weekly_deliver(user)
end

Front 395

How to start a batch find from a specific primary key

Back 395

User.find_each(:batch_size => 5000, :start => 2000) do

Front 396

What is the diff between find_each and find_in_batches?

Back 396

find_in_batches yields arrays of models (each array of batch size) instead of a singular item like find_each

# Works in chunks of 1000 invoices at a time. Invoice.find_in_batches(:include => :invoice_lines)

Front 397

find all clients where the orders_count field’s value is 2.

Back 397

Client.where("orders_count = '2'")

Front 398

when using the AR where clause with one condition be sure to wrap it in ....

Back 398

quotes "...."

Client.where("orders_count = '2'")

Front 399

when using the where clause and looking for equal do you use single or double equals?

Back 399

single

Client.where("orders_count = '2'")

Front 400

when using AR where clause with an argument that varies what do you do?

Back 400

wrap the entire clause in an [], with the first element being the condition (substituting a ? for the variable), and the second condition being the variable to substitute in

Client.where(["orders_count = ?", params[:orders]])

Front 401

how to specify two variables with AR where clause

Back 401

use two questions marks and pass in three elements total to the clause (last two being the variables values)

Client.where(["orders_count = ? AND locked = ?", params[:orders], false])

Front 402

Why write code like
Client.where(["orders_count = ?", params[:orders]])

instead of

Client.where("orders_count = #{params[:orders]}")

Back 402

rgument safety. Putting the variable directly into the conditions string will pass the variable to the database as-is. This means that it will be an unescaped variable directly from a user who may have malicious intent.

Front 403

Give an alternative way to write this using hashes

Client.where(["orders_count = ?", params[:orders]])

Back 403

Client.where(["orders_count = :order_count", {:orders_count => params[:orders]}])

#useful where large number of vars as it aids readability

Front 404

If you’re looking for a range inside of a table (for example, users created in a certain timeframe) what sql are you looking for

Back 404

#IN

... WHERE (created_at IN ('2007-12-31','2008-01-01','2008-01-02','2008-01-03')

Front 405

If you’re looking for a range inside of a table (for example, users created in a certain timeframe) what AR would you use

Back 405

Client.where(["created_at IN (?)", (params[:start_date].to_date)..(params[:end_date].to_date)])

#note the "...IN (?)"
#and the (start)...(end)

Front 406

What is the general structure for a range query

Back 406

MOdel.where(["field AT (?)", (value)..(value2)
])

Front 407

How to find clients created after a certain date?

Back 407

#pass in a greater than sql sign to the query

Client.where( ["created_at > ? A", params[:start_date]] )

Front 408

How to use a hash condition to search for locked clients (boolean)

Back 408

Client.where({ :locked => true })

Front 409

Client.where({ :locked => true }) can also be written as...

Back 409

a string instead of a sybmol

Client.where({ 'locked' => true })

Front 410

Never pass a ... object to sql

Back 410

Time object

it will attempt to compare your field to every second in that range resulting in **** loads of queries

Front 411

How to find all the clients who have 1,3 or 5 orders?

Back 411

Client.where({ :orders_count => [1,3,5] })

Front 412

What is the sql for Client.where({ :orders_count => [1,3,5] })

Back 412

SELECT * FROM clients WHERE (clients.orders_count IN (1,3,5))

Front 413

Get a set of records and want to order them in ascending order by the created_at field in your table:

Back 413

Client.order("created_at")

Front 414

Get clients in descending order of created at

Back 414

Client.order("created_at DESC")

Front 415

Get clients in ascending order of created at

Back 415

Client.order("created_at ASC")

Front 416

How to order by multiple fields

Back 416

Pass them in as elements separated by commas to the order condition

Client.order("orders_count ASC, created_at DESC")

Front 417

How to to select only viewable_by and locked columns:

Back 417

Client.select("viewable_by, locked")

Front 418

What is the consequence of using the select AR method

Back 418

If the select method is used, all the returning objects will be read only.

Front 419

What sql does this create:
Client.select("viewable_by, locked")

Back 419

SELECT viewable_by, locked FROM clients

Front 420

When using select If you attempt to access a field that is not in the initialized record you’ll receive:

Back 420

ActiveRecord::MissingAttributeError: missing attribute: <attribute>

Where <attribute> is the attribute you asked for.

Front 421

How to grab a single record per unique value in a certain field - i.e. only get the differing names

Back 421

pass in sql DISTINCT(attr_name) to the select

Client.select("DISTINCT(name)")

Front 422

How to limit a query to only 5 matches

Back 422

Client.limit(5)

Front 423

What sql does this create:

Client.limit(5)

Back 423

SELECT * FROM clients LIMIT 5, 5

Front 424

How to get records starting from only the 100 record in the table

Back 424

Client.offset(100)

Front 425

What sql does this create:

Client.limit(5).offset(100)

Back 425

SELECT * FROM clients LIMIT 5, 100

Front 426

if you want to find a collection of the dates orders were created on: (where there are multiple orders per date sometimes and none othertimes)

Back 426

Order.group("date(created_at)")

Front 427

How to explicitly disallow modification/destruction of the matching records returned in a Relation object,

Back 427

Client.first.readonly(true)

Front 428

what happens if you try to modify a read only attribute

Back 428

ActiveRecord::ReadOnlyRecord exception:

Front 429

Optimistic locking works by...

Back 429

checking whether another process has made changes to a record since it was opened returning an ActiveRecord::StaleObjectError exception

Front 430

If you try to update something which someone else is already updating (and optimistic locking is on) what happens?

Back 430

ActiveRecord::StaleObjectError exception
and the udpate is ignored

Front 431

for optimistic locking to work...

Back 431

the table needs to have a column called lock_version.

Front 432

You must ensure that your database schema defaults the lock_version column to

Back 432

0.

Front 433

How to stop locking once set up?

Back 433

ActiveRecord::Base.lock_optimistically = false.

Front 434

How to override the name of the lock_version column

Back 434

class Client < ActiveRecord::Base set_locking_column :lock_client_column
end

Front 435

Pessimistic locking uses

Back 435

locking mechanism provided by the underlying database

Front 436

How to use pessimistic looking?

Back 436

On a per find basis

Passing :lock => true to Model.find obtains an exclusive lock on the selected rows

Item.first(:lock => true)

Front 437

How to do an inner join on categories and posts

Back 437

Category.joins(:posts)

Front 438

How to do an inner join on categories and posts AND comments (3 way)

Back 438

Post.joins(:category, :comments)

Front 439

How to specify conditions on a join table - e.g. Client calling join or orders but requires it within a certain (predefined) timerange

Back 439

Client.joins(:orders).where(:orders => {:created_at => time_range})

#note the use of symbol with the join table name within the where condition and using a hash as the value

Front 440

How many queries does this execute?

clients = Client.all(:limit => 10)

clients.each do |client|
puts client.address.postcode
end

Back 440

xecutes 1 ( to find 10 clients ) + 10 ( one per each client to load the address ) = 11 queries in total.

classic n+1 problem

Front 441

what method is used to get around the n+1 problem

Back 441

includes

clients = Client.includes(:address).limit(10)

now looping through clients.address doesn't require extra queries

Front 442

How many queries does this execute?

clients = Client.includes(:address).limit(10)

clients.each do |client|
puts client.address.postcode
end

Back 442

Only 2

SELECT * FROM clients LIMIT 10 SELECT addresses.* FROM addresses WHERE (addresses.client_id IN (1,2,3,4,5,6,7,8,9,10))

Front 443

How to eager load any possible number of associations with a single Model.find

Back 443

Post.includes(:category, :comments)

Front 444

If you have a field called first_name on your Client model for example, you get what 3 dynamic finder methods for free??

Back 444

find_by_first_name
find_all_by_first_name
find_last_by_first_name

# note the LAST

Front 445

Whats the diff between

Client.find_by_name("Ryan")
and
Client.find_by_name!("Ryan")

Back 445

specifying a ! at the end gets dynamic finders to raise ActiveRecord::RecordNotFound error if they do not return any records

Front 446

How to create/initialize objects if they aren’t found.

Back 446

find_or_create_by_first_name(params[:first_name])

Front 447

How does this work:

find_or_create_by_first_name(params[:first_name])

Back 447

will firstly perform a find and then create if the find returns nil.

Front 448

diff between

find_or_initialize_by_attr_name
and
find_or_create_by_attr_name

Back 448

initialize is like calling new(doesnt save to db), whereas create is calling create (and saves to db)

Front 449

How to simply want to check for the existence of the object without returning it

returns true or fals

Back 449

Client.exists?(1)
#where 1 is the id

Front 450

how to specify conditions with the exists? method

Back 450

Client.exists?(:conditions => "first_name = 'Ryan'")

Front 451

How to count number of items in db (makes a fresh call)

Back 451

count method
Client.count(:conditions => "first_name = 'Ryan'")

Front 452

diff between .size and .count

Back 452

.count always calls db afresh, .size wont if realationship is already populated

Front 453

How many clients in Client table?

Back 453

Client.count

Front 454

How many clients in Client table who have given their age attribute?

Back 454

Client.count(:age).

Front 455

How to get the average of the orders_count attr?

Back 455

Client.average("orders_count")

Front 456

How to get the minimum of the age attr?

Back 456

Client.minimum("age")

Front 457

How to get the maximum of the age attr?

Back 457

Client.maximum("age")

Front 458

How to get the sum of all the orders_count fields on all the records

Back 458

Client.sum("orders_count")

Front 459

how to evoke rails server (previously script/server)

Back 459

rails server

Front 460

how to get help in any rails command line utility

Back 460

append -h or --help

Front 461

how to evoke rails console (previously script/console)

Back 461

rails console

Front 462

How to drop into whichever db your using's command line interface (SQL< PosgreSQL whatever)

Back 462

rails dbconsole

Front 463

how to add a plugin

Back 463

rails plugin http://wherever

Front 464

how to undo a model generate for Opps

Back 464

rails destroy model Oops

Front 465

what does destroy do

Back 465

It’ll figure out what generate did, and undo it.

Front 466

How to check ruby version number?

Back 466

rake about

Front 467

How to check Rails version?

Back 467

rake about

Front 468

How to check migration schema?

Back 468

rake about

Front 469

How to use a different server for rails?

Back 469

install its gem (e.g. gem install mongrell)

then call
rails server mongerl

Front 470

See all rake task available?

Back 470

rake -T

Front 471

rake db:create
rake db:charset
rake db:migrate

what do these ahve in common

Back 471

all are namespaced by db

Front 472

what is rake:notes for

Back 472

earch through your code for commented lines beginning with “FIXME”, “OPTIMIZE”, “TODO”, or any custom annotation (like XXX) and show you them.

Front 473

what is rake docs for

Back 473

strip out or rebuild any of the Rails documentation (including this guide!),

Front 474

view all timezones rails know about

Back 474

rake time:zones:all

Front 475

remove tmp files

Back 475

rake tmp:clear

Front 476

see stats such as test ratio and LOC

Back 476

rake stat

Front 477

see all defined routes

Back 477

rake routes

Front 478

when rails receives an incoming request like

GET /patients/17

what does it do

Back 478

it asks the router to match it to a controller action. thus the dsl

match "/patients/:id" => "patients#show"

Front 479

how does the routing system represent variables in the url

Back 479

prepend a :
e.g. patients/:id

Front 480

Resource routing allows you to

Back 480

quickly declare all of the common routes for a given resourceful controller

resources :photos

#instead of sep route for index, show etc.

Front 481

Index action is what url and verb

Back 481

GET /photos
#same as create except a GET

Front 482

New action is what url and verb

Back 482

GET /photos/new
#note it's get as nothing is posted yet (its still new)

#note too the necessity of adding the /new (only other with an extra word is edit)

Front 483

Create action is what url and verb

Back 483

POST /photos

#same as index except a POST

Front 484

Show action is what url and verb

Back 484

GET /photos/:id

#even though your getting a singular item it's still photos

Front 485

Edit action is what url and verb

Back 485

GET /photos/:id/edit


#even though your getting a singular item it's still photos

Front 486

Update action is what url and verb

Back 486

PUT /photos/:id


#even though your getting a singular item it's still photos

Front 487

Delete action is what url and verb

Back 487

DELETE /photos/:id


#even though your getting a singular item it's still photos

Front 488

what discrepancy exists between the helper for the show path and the way the url is written

Back 488

photo_path(id) - singular photo
photos/:id - plural photo

Front 489

helper for new or edit photo

Back 489

new_photo_path
edit_photo_path

Front 490

Give an example of a resource that clients will ook up with referencing an ID (ie a show without an id)

Back 490

/profile always shows the profile of the currently logged in user.

Front 491

how to create a singular resouce, i.e. one with no index action

Back 491

resource :geocoder

instead of

resources :geocode

Front 492

How to organize controllers under an Admin:: namespace

Back 492

namespace "admin" do
resources :posts, :comments
end

Front 493

If you had this code where would you palce the posts and comments controllers

namespace "admin" do
resources :posts, :comments
end

Back 493

app/controllers/admin

Front 494

what does the photos index path look like

namespace "admin" do
resources :posts, :comments
end

Back 494

admin_photos_pah

#admin is singular just as it was defined in the namespac

Front 495

what does the photos edit path look like

namespace "admin" do
resources :posts, :comments
end

Back 495

edit_admin_photo_path(id)

#edit prepends all, but straight after is admin art

Front 496

what does the index url for photso look like

namespace "admin" do
resources :posts, :comments
end

Back 496

/admin/photos

#/admin in front

Front 497

f you want to route /photos (without the prefix /admin) to Admin::PostsController, you could use

Back 497

#use the scope :module => "namespace" construction

scope :module => "admin" do
resources :posts, :comments
end

Front 498

For a single case whats a quicker way of writing

scope :module => "admin" do
resources :posts, :comments
end

Back 498

#omit the scope and must do :module => "namespace"

resources :posts, :module => "admin"

Front 499

If you want to route /admin/photos to PostsController (without the Admin:: module prefix), you could use

Back 499

#use scope with a url as the first argument instead

scope "/admin" do
resources :posts, :comments
end

Front 500

Quicker way of writing

scope "/admin" do
resources :posts, :comments
end

Back 500

resources :posts, :path => "/admin"

Front 501

HOw to capture nested resources in routing?

Back 501

resources :magazines do
resources :ads
end

Front 502

How to see a list of all magazines?

resources :magazines do
resources :ads
end

Back 502

/magazines/1/ads

Front 503

How to see a display a specific ad belonging to a specific magazine

resources :magazines do
resources :ads
end

Back 503

/magazines/1/ads/1

Front 504

How to return an HTML form for creating a new ad belonging to a specific magazine

resources :magazines do
resources :ads
end

Back 504

/magazines/1/ads/new

Front 505

Resources should never be nested more than ....

Back 505

1 level deep.

Front 506

When using magazine_ad_path, you can pass in..... instead of the numeric IDs.

Back 506

instances of Magazine and Ad

magazine_ad_path(@magazine, @ad)

Front 507

shortest link_to for the show path of a specific magazine

Back 507

<%= link_to "Magazine details", @magazine %>

Front 508

shortest link_to for the show path of a specific ad nested in a specific magazine

Back 508

<%= link_to "Ad details", [@magazine, @ad] %>

#note the array used to store all the values within the second argument

Front 509

how to add an additional route which acts on an individual member of a resource collection (imagine we had a preview action on a photo controller)

Back 509

resources :photos do
get :preview, :on => :member
end

Front 510

how to add an additional route which acts on the collection of a resource (imagine we had a search action on a photo controller)

Back 510

resources :photos do
collection do
get :search
end
end

Front 511

Structure of an additional route which acts on an individual member of a resource collection

Back 511

inside the resources block
verb :method_name :on => :member

e.g. get :preview, :on => :member

Front 512

Structure of an additional route which acts on a collection of a resource collection

Back 512

inside the resource block
get :search, :on => :collection

Front 513

Dif between member and collection resource route additions

Back 513

collection r has an additional :on => :collection arg


member has an additional :on => :member arg

verb :method_name :on => :member

Front 514

If you find yourself adding many extra actions to a resourceful route, it’s time to

Back 514

stop and ask yourself whether you’re disguising the presence of another resource.

Front 515

How to make part of a route optional

Back 515

surround it with (/ ) where the closing parenthiss continues till the end of the route

match ':controller(/:action(/:id))'

Front 516

match ':controller/:action/:id/:user_id'

what params are available

Back 516

params[:id]
and
params[:user_id]

Front 517

shortest link_to for the show path of a specific magazine

Back 517

<%= link_to "Magazine details", @magazine %>

Front 518

shortest link_to for the show path of a specific ad nested in a specific magazine

Back 518

<%= link_to "Ad details", [@magazine, @ad] %>

#note the array used to store all the values within the second argument

Front 519

how to add an additional route which acts on an individual member of a resource collection (imagine we had a preview action on a photo controller)

Back 519

resources :photos do
get :preview, :on => :member
end

Front 520

how to add an additional route which acts on the collection of a resource (imagine we had a search action on a photo controller)

Back 520

resources :photos do
collection do
get :search
end
end

Front 521

Structure of an additional route which acts on an individual member of a resource collection

Back 521

inside the resources block
verb :method_name :on => :member

e.g. get :preview, :on => :member

Front 522

Structure of an additional route which acts on a collection of a resource collection

Back 522

inside the resource block
get :search, :on => :collection

Front 523

Dif between member and collection resource route additions

Back 523

collection r has an additional :on => :collection arg


member has an additional :on => :member arg

verb :method_name :on => :member

Front 524

If you find yourself adding many extra actions to a resourceful route, it’s time to

Back 524

stop and ask yourself whether you’re disguising the presence of another resource.

Front 525

How to make part of a route optional

Back 525

surround it with (/ ) where the closing parenthiss continues till the end of the route

match ':controller(/:action(/:id))'

Front 526

match ':controller/:action/:id/:user_id'

what params are available

Back 526

params[:id]
and
params[:user_id]

Front 527

How can specify what Rails should route "/" to?

Back 527

root :to => 'pages#main'

Front 528

Give an example of a static segment within a route

Back 528

match ':controller/:action/:id/with_user/:user_id'

Front 529

what params does this have

/photos/show/1?user_id=2

Back 529

{ :controller => “photos”, :action => “show”, :id => “1”, :user_id => “2” }.

query string is converted to a param

Front 530

How to get params[:format] as "jpg" without specifying a dynamic segment in the route

Back 530

match 'photos/:id' => 'photos#show', :defaults => { :format => 'jpg' }

Front 531

how to give a route a custom name?

Back 531

massing the :as => :name option

match 'exit' => 'sessions#destroy', :as => :logout

Front 532

what two things does this generate?

match 'exit' => 'sessions#destroy', :as => :logout

Back 532

logout_path helper

and the url /logour

Front 533

How to to enforce a format for a dynamic segment:

Back 533

passing a constrainsts => { :param_name => /regex/ } option

match 'photo/:id' => 'photos#show', :constraints => { :id => /[A-Z]\d{5}/ }

Front 534

more succint way to express


match 'photo/:id' => 'photos#show', :constraints => { :id => /[A-Z]\d{5}/ }

Back 534

match 'photo/:id' => 'photos#show', :id => /[A-Z]\d{5}/

Front 535

:constraints takes regular expression. However note that .... can’t be used within constraints.

Back 535

regexp anchors

thus this wont work

match '/:id' => 'videos#show', :constraints => {:id => /^\d/}

Front 536

how to use globbing to match photo/long/path/to/12, setting params[:other] to "long/path/to/12".

Back 536

match 'photo/*other' => 'photos#unknown'

Front 537

how to redirect from /stories to the post controller?

Back 537

match "/stories" => redirect("/posts")

Front 538

how to redirect from /stories to the poast controller - this time passing over dynamic segments

Back 538

match "/stories/:name" => redirect("/posts/%{name}")

#note the interpopated ruby within the match string which mirrors the original symbol

Front 539

how to have a url say one thing yet use a different controller (resourceful)

Back 539

resources :photos, :controller => "images"

Front 540

resources :photos, :controller => "images"

what are the helpers here

Back 540

still
photos_path etc.

Front 541

how to specify constraints for a restful url?

Back 541

resources :photos, :constraints => {:id => /[A-Z][A-Z][0-9]+/}

Front 542

How to override the normal naming for the named route helpers.

Back 542

#an as option which has the string to rename the named routes with

resources :photos, :as => "images"

gives you url or /photos but helpers of images_path

Front 543

how to verride the automatically-generated “new” and “edit” segments in URLs:

Back 543

#a path_names option which has a hash with :new and :edit mapped to their new names

resources :photos, :path_names => { :new => 'make', :edit => 'change' }

Front 544

how to limit the routes created for a resource to only index and show

Back 544

resources :photos, :only => [:index, :show]

Front 545

How to specify a list of routes that Rails should not create for a resource?

Back 545

resources :photos, :except => :destroy

Front 546

Advantage of using :only and :except on resource routes?

Back 546

can cut down on memory use and speed up the routing process.

Front 547

Callbacks allow you to ....

Back 547

to trigger logic before or after an alteration of an object’s state.

Front 548

Validations ensure that....

Back 548

only valid data is stored in your database.

Front 549

Client side validations (with JS) can be a ...

Back 549

convenient way to provide users with immediate feedback as they use your site.

Front 550

What are the two kinds of Active Record objects:

Back 550

those that correspond to a row inside your database and those that do not.

Front 551

AR uses what instance method to determine whether an object is already in the database or not?

Back 551

new_record?

Front 552

how to create a person object with name attr John Doe?

Back 552

Person.new(:name => "John Doe")

Front 553

Using save! or create! or update_attributes! what happens if a record is invalid?

Back 553

exception raised

Front 554

Using save or update_attributes what happens if a record is invalid?

Back 554

save and update attributes return false

Front 555

Using create or update what happens if a record is invalid?

Back 555

you get the original object

Front 556

how to bypass validations with save

Back 556

save(false)

Front 557

What special behaviour do the following have vis a vis validations?

# update_all
# update_attribute

Back 557

they don't run validations

#note that whilst udpate_attribute doesnt validate, update_attributes does

Front 558

What method triggers your validations and returns true if no errors were added to the object, and false otherwise.

Back 558

valid?

Front 559

bject instantiated with new wil ... even if it’s technically invalid, because validations are not run when using new.

Back 559

not report errors

Front 560

how to see the errors on an object in the console

Back 560

p.errors

Front 561

What method triggers your validations and returns true if any errors were added to the object, and

Back 561

invalid?

Front 562

How do you verify whether or not a particular attribute of an object is valid

Back 562

>> Person.new.errors[:name].any? # => false

Front 563

What important difference is there between Persion.errors[:name] and Person.valid?

Back 563

errors[:attr] doesnt trigger validations - only checks if errors found on object

Front 564

What 3 options does the :on option take in validation helpers?

Back 564

:save (the default), :create or :update

Front 565

Validates that a checkbox on the user interface was checked when a form was submitted.

Back 565

validates_acceptance_of :terms_of_service

Front 566

How does validates_acceptance_of :field work with your db?

Back 566

‘acceptance’ does not need to be recorded anywhere in your database (if you don’t have a field for it, the helper will just create a virtual attribute).

Front 567

How to specify a custom message in validations?

Back 567

:message option

Front 568

How to check if associated objects are validated?

Back 568

validates_associated :books

. When you try to save your object, valid? will be called upon each one of the associated objects.

Front 569

Why should you not use validates_associated on both ends of your associations,?

Back 569

they would call each other in an infinite loop.

Front 570

What helper when you have two text fields that should receive exactly the same content.

Back 570

validates_confirmation_of :email

Front 571

What field name does validates_confirmation_of :email expect?

Back 571

irtual attribute whose name is the name of the field that has to be confirmed with “_confirmation” appended.

thus email_confirmation

Front 572

In what case is the validations_confirmation_of not run?

Back 572

when email_confirmation is nil

[to enforce add v_p_o :email_confirmation

Front 573

validates that the attributes’ values are not included in a given set.

Back 573

validates_exclusion_of :subdomain, :in => %w(www),

Front 574

validates_exclusion_of helper, what option receives the set of values which won't be accepted

Back 574

:in => %w(www)

Front 575

validates the attributes’ values by testing whether they match a given regular expression,

Back 575

validates_format_of :legacy_code, :with => /\A[a-zA-Z]+\z/

Front 576

with validations_format_of, what option receives the regex to validate against

Back 576

:with => /\A[a-zA-Z]+\z/,

Front 577

validates that the attributes’ values are included in a given set (opposite of validations_exclusion_of)

Back 577

validates_inclusion_of :size, :in => %w(small medium large)

Front 578

validates the length of the attributes’ values

Back 578

validates_length_of :name, :minimum => 2

Front 579

how to require at validations an exact length for an input?

Back 579

validates_length_of :registration_number, :is => 6

Front 580

how to require at validations a minimum length for an input?

Back 580

validates_length_of :bio, :maximum => 500

Front 581

how to require at validations a maximum length for an input?

Back 581

validates_length_of :bio, :maximum => 500

Front 582

how to require at validations a range for an input?

Back 582

validates_length_of :password, :in => 6..20

Front 583

In validates_lenth)of what is used as a placeholder for the number corresponding to the length constraint being used.

Back 583

%{count}

:too_long => "%{count} characters is the maximum allowed"

Front 584

validates_size_of is an alias for

Back 584

validates_length_of

Front 585

validates that your attributes have only numeric value

Back 585

validates_numericality_of

Front 586

How to make sure only whole numbers?

Back 586

validate_numericality of :field, :only_integer => true

Front 587

How to ensure only odd numbers are entered?

Back 587

validates_numericality_of :points, :odd => true

Front 588

How to ensure only points greater than 10 are entered?

Back 588

validates_numericality_of :points, :greater_than => 10

Front 589

How to ensure points less than 40 are entered?

Back 589

validates_numericality_of :points, :less_than => 40

Front 590

How to ensure points exactly equal to 4 are entered?

Back 590

validates_numericality_of :points, :equal_to => 4

Front 591

How to ensure points greater than or equal to 23 are entered?

Back 591

validates_numericality_of :points greater_than_or_equal_to => 23

Front 592

validates that the specified attributes are not empty

Back 592

validates_presence_of :name, :login, :email

Front 593

blank? (which is used in validates presence of) checks if the value is either

Back 593

nil or a blank string

Front 594

ou want to be sure that an association is present, you’ll need to test whether the

Back 594

foreign key used to map the association is present, and not the associated object itself.

validates_presence_of :order_id

Front 595

validates that the attribute’s value is unique right before the object gets saved

Back 595

validates_uniqueness_of :email

Front 596

How does validates_uniqueness_of work?

Back 596

e validation happens by performing a SQL query into the model’s table, searching for an existing record with the same value in that attribute

Front 597

What step should you also take in using validates_uniqueness_of to protect against having two dif db connectsion making two records with same value you intend to be unique?

Back 597

create a unique index in your db

Front 598

In validates_uniqueness_of how do you specify other attributes that are used to limit the uniqueness check:

Back 598

set a scope option

validates_uniqueness_of :name, :scope => :year,

Front 599

In validates_uniqueness_of how do you define whether the uniqueness constraint will be case sensitive or no

Back 599

validates_uniqueness_of :name, :case_sensitive => false

Front 600

default setting of validates_uniqueness_of case sensitivity option

Back 600

true - i.e. it is case sensitive

Front 601

How to define a custom validator

Back 601

validates_with GoodnessValidator

#where goodness validator inherits from ActiveRecord::Validator class within which a validate method is defined

Front 602

What class do validators inherit from?

Back 602

class GoodnessValidator < ActiveRecord::Validator

Front 603

How do custom validators made with validates_with access the original AR object

Back 603

the record variable

def validate
if record.first_name == "Evil"
record.errors[:base] << "This person is evil" end

Front 604

How to add custom errors within a custom validation

Back 604

record.errors[:base] << "This person is evil" end

Front 605

How to specify when a validation is run with a block rather than a separate validation class?

Back 605

validates_each

validates_each :name, :surname do |model, attr, value|

model.errors.add(attr, 'must start with upper case') if value =~ /\A[a-z]/

Front 606

skips the validation when the value being validated is nil

Back 606

:allow_nil => true

validates_inclusion_of :size, :in => %w(small medium large), :allow_nil => true

Front 607

skips the validation when the value being validated is nil OR AN EMPTY STRING

Back 607

:allow_blank => true

validates_length_of :title, :is => 5, :allow_blank => true

Front 608

validation only run on create

Back 608

validates_uniqueness_of :email, :on => :create

Front 609

validation only runs on update

Back 609

validates_numericality_of :age, :on => :update

Front 610

validation only runs on save

Back 610

validates_presence_of :name, :on => :save

Front 611

how to make a validation happen only conditionally

Back 611

using :if or :unless options

Front 612

specify when the validation should happen.

Back 612

validates_presence_of :card_number, :if => :paid_with_card?

Front 613

specify when the validation should not happen

Back 613

validates_presence_of :card_number, :unless => :paid_with_cash?

Front 614

:if and :unless validation options take what three values

Back 614

symbols (which point to other methods defined below)
strings (which contain Ruby code which will be called with Eval)
Procs

Front 615

how to use a string to require that a vaidation only runs if name is nil

Back 615

validates_presence_of :surname, :if => "name.nil?"

Front 616

how to pass a proc to a validation condition

Back 616

validates_confirmation_of :password, :unless => Proc.new { |a| a.password.blank? }

Front 617

how to run chains of custom validations

Back 617

#call validate with symbols of each of the custom validation methods

validate :expiration_date_cannot_be_in_the_past, :discount_cannot_be_greater_than_total_value

Front 618

how to add custom errors within custom validations?

Back 618

#errors.add(:field, "message")

errors.add(:discount, "can't be greater than") if ....

Front 619

How to acess the field in a custom validation

Back 619

Use the field name as is. For example if expiration date

errors.add(...) if expiration_date < Date.today

Front 620

Custom validations are .... to a particular field name

Back 620

not tied - thus they can access any of the field names (or multiple fields)

Front 621

How to create your own validation helpers (e.g. validates_choice_of :field)

Back 621

ActiveRecord::Base.class_eval do

def self.validates_as_choice (attr_name, n, options={})
....
end
end

Front 622

In creating custom validation helpers where does the helper name appear

Back 622

def self.helper_name

e.g.
def self.validates_as_choice

Front 623

within what block do you define custom validation helpers

Back 623

ActiveRecord::Base.class_eval do

Front 624

How to uninstall all older versions of gems

Back 624

gem cleanup

Front 625

where has the error_messages or error_messages_for helper method gone in rails3?

Back 625

out of core, into a plugin called dynamic_form

reasoning - most people want to customize how error messages are displayed

Front 626

why you probably won't need error_messages helpers anymore?

Back 626

as now they are shown in plain html and are easily formatted. - you can always pull them into a partial (shared/error_messages)

Front 627

how to put error messages generated stuff into a partial

Back 627

render "shared/error_messages", :target => @user

then use target within the partial

#note - 1 render doesn't require partial
2 the partial name doesnt need to be preceded by _ when called here
3 a @user object can be passed directly

Front 628

how to get an array of validators on a given model from the console

Back 628

Model.validators

User.validators

Front 629

how to get an array of validators on a specific trait of a given model from the console

Back 629

Model.validators_on(:attr)

User.validators_on(:email)

Front 630

code to check if a presence of validator is on a given trait

Back 630

@user.class.validators_on(:email).map(&:class).include? ActiveModel::Validations::PresenceValidator

Front 631

how can you express this more concisely

validates_presence_of :email
validates_uniqueness_of :email
validates_format_of :email

Back 631

#validates :attr, :validator => true, :validator2 => true, :validator3 => {hash of options}

validates :email, :presence => true, :uniqueness => true, :format => {:with => //}

Front 632

where would you store a custom validator

Back 632

in the lib folder

Front 633

what class does a custom validator inherir from

Back 633

ActiveModel::EachValidator

Front 634

What method does a class inheriting from ActiveModel::EachValidator expect you to define?

Back 634

validate_each

Front 635

what args does validate_each require

Back 635

(object, attribute, value)

Front 636

how to add an error to an object within the validates_each method?

Back 636

objects.errors[attribute] << "msg" if value != //

Front 637

How to include a constant in a model somewhere else in the rails app

Back 637

Modelname::Constant

NOT

MODELNAME::CONSTANT

Front 638

How to default to blank in a select box or date helper

Back 638

:include_blank => true

Front 639

How to set the order of day/month/year in a date select helper

Back 639

#the order option which takes an array of day month year

f.date_select :start_date, :order => [:day, :month, :year]

Front 640

How to exclude day (etc.) in a date select helper

Back 640

#set :discard_day => true

f.date_select :start_date, :discard_day => true

Front 641

How to go back to previous version of a migration

Back 641

rake db:rollback

Front 642

what is named scope know as in rails 3

Back 642

scope - its rebuilt on the new AR Relation class (where, order etc.)

No longer are they a slightly different construct than your normal query methods. They are now built upon the very same query methods that you would use were you to execute a query directly.

Front 643

what is the lambda's purpose here:

scope :published, lambda {
where("posts.published_at IS NOT NULL AND posts.published_at <= ?", Time.zone.now)
}

}

Back 643

delays evaluation of the Time.zone.now argument until when the scope is invoked (otherwise time used would be that when CLASS was first evaluated not scope itself)

Front 644

Scope for posts published (i.e. published date greater than now)

Back 644

scope :published, lambda {
where("posts.published_at <= ?", Time.zone.now)
}

#note - first param is scope name
# second param is a lambda which takes { } with conditions inside

Front 645

within a scope what format do the conditions inside a lambda take

Back 645

ar_word("table.column <= ?", substitue for question)

lambda {
where("posts.published_at <= ?", Time.zone.now)
}

Front 646

within a scope how to make sure something is not a null value

Back 646

where("posts.published_at IS NOT NULL AND .....")

Front 647

how to get a scope to order by posts published at date?

Back 647

scope :recent, order("posts.published_at DESC")

Front 648

what feature of scopes does this show:

scope :recent, published.order("posts.published_at DESC")

#note that published is a scope defined already above

Back 648

the chainability of scopes within scope definitions

#note how the predefined scope is used in the second param and then new query scopes are chained to it

Front 649

what feature does this code show?

class Post < ActiveRecord::Base

class << self
def search(q)
query = "%#{q}%"
where("posts.title LIKE ?", query).where("posts.body LIKE ?", query)
end
end
end

Back 649

creating a method (rather than a scope) which uses the AR scope query language and can be chained to scopes

now you can do queries like:

Post.search('w').order('created_at DESC').limit(2).published

Front 650

how do you do a cross model scope - e.g. User model - all users who have commented on a post

Back 650

#use the joins query stuff

scope :commented, joins(:comments).group("users.id")

Front 651

what is the format of a joins query (SQL)

Back 651

join table1 on table1.column_name= table1.column_name - where column_name is often id

joins("join comments on comments.user_id = users.id")

Front 652

How do you get an array of a certain attribute of a model across many models?

e.g. the view_count for all posts

Back 652

Post.collect(&:view_count)

#note 1 use of the collect method
#note 2 & then : then attrib_name

Front 653

How to perform an action on a set of models found with a scope? - e.g. increment the views count on all publichsed Posts

Back 653

Post.published.update_all("views_count = views_count + 1")

#call update_all on the scoped set
#update_all takes a string which will be evaled to logic
#update all takes one of the attrs in it's logic

Front 654

How to destroy all unpublisehd posts (where unpublished is just a scope)

Back 654

Post.unpublished.destroy_all

Front 655

How to build objects from a given scope?
E.g. build psots with title Luda here

scope :titled_luda, where(:title => 'Luda')

Back 655

Post.titled_luda.build

#thus scopes are now both packages of query and constructino logic

Front 656

which one of these will not work in builder methods?

scope :titled_luda, where(:title => 'Luda')

scope :title_luda, where("title = 'Luda'")

Back 656

the second one - you must always use the hash form of where for builders to work

where(:title => "luda")

Front 657

How to find all Users in order of descending user id

Back 657

#order(tablename.id DESC)
# note the space between the table.col and DESC or ASC

User.order('users.id DESC')

Front 658

How to modify all shirt items so their color attr is now black?

Back 658

Shirt.update_all :colour => 'black'

Front 659

How to create a scope which takes a time variable and finds the items published since then

Item.since(time)

Back 659

scope :since, lambda {|time| where("created_at > ?", time)}

#note use of lamba {|var| where(" ?", var) } structure

Front 660

Whats wrong with this is rails 3

scope :since, lambda {|time| {:conditions => ["created_at > ?", time] }}

Back 660

options hash will be deprecated in Rails 3.1 (i.e. the {:conditions ****}

replace with where() clause etc.

Front 661

In Rails 3, the Application itself, the router, and controller actions themselves are all .... applications.

Back 661

rack

#thus you can also insert standard Rack middleware in config.ru, in your Rails application, in the router, or even in a controller’s action

Front 662

ActionController and ActionMailer to inherit from a common superclass: ....

Back 662

AbstractController.

#This means that ActionMailer can no longer drift away from ActionController, leaving us with two distant cousin APIs.

Front 663

Rails 3..... allowing developers to convert Strings into safe Strings easily

Back 663

escapes all Strings,

thus no need to worry about XSS protection as before

Front 664

what does integrating ntegrating Nick Kallen’s ActiveRelation codebase mean?

Back 664

you can chain queries for refinement before Rails builds the actual SQL query.

For instance, instead of Post.scoped immediately connecting to the database and retrieving all posts, it creates a relation object representing the idea of “all posts”. You can then refine further, such as Post.scoped.where(:author => "Yehuda"). This means that you can pass around relations, refining them as appropriate in helper methods before the view finally kicks off the query when it iterates over the objects.

Front 665

A Rails 3 application is an object (of the class

Back 665

Rails::Application

#also doubles as a valid Rack application

Front 666

adding a member or collection to a resouce gives you what

Back 666

a url helper method of the format

method_name_model_name_path

e.g. preview_photo_path

Front 667

when creating custom validation methods what are the alternatives to plain old validate :method_name

Back 667

validate_on_create or validate_on_update

Front 668

If you were to create a validator helper (which inherits from ActiveRecord::Base) where woud you put it?

Back 668

in config/initializers.

Front 669

How to add errors messages that are related to the object’s state as a whole, instead of being related to a specific attribute

Back 669

errors.add_to_base("This person is invalid because ...")

Front 670

What params does errors.add_to_base have?

Back 670

only one - the message to be displaye

Front 671

How to add error messages that are related to particular attribute

Back 671

errors.add(:name, "cannot contain the characters !@#%*()_-+=")

Front 672

What params does errors.add take?

Back 672

two
first - :attr_name
second - msg

Front 673

How to see the errors on a particular attribute

Back 673

person.errors.on(:name) # => "cannot contain the characters !@#%*()_-+="

Front 674

How to see the errors on a particular attribute as seen in the form displayed to a user (ie. attr name appeneded)

Back 674

person.errors.full_messages # => ["Name cannot contain the characters !@#%*()_-+="]

Front 675

person.errors.on(:name) returns what if there are no errors?

Back 675

nil

Front 676

adding a member or collection to a resouce gives you what

Back 676

a url helper method of the format

method_name_model_name_path

e.g. preview_photo_path

Front 677

when creating custom validation methods what are the alternatives to plain old validate :method_name

Back 677

validate_on_create or validate_on_update

Front 678

If you were to create a validator helper (which inherits from ActiveRecord::Base) where woud you put it?

Back 678

in config/initializers.

Front 679

How to add errors messages that are related to the object’s state as a whole, instead of being related to a specific attribute

Back 679

errors.add_to_base("This person is invalid because ...")

Front 680

What params does errors.add_to_base have?

Back 680

only one - the message to be displaye

Front 681

How to add error messages that are related to particular attribute

Back 681

errors.add(:name, "cannot contain the characters !@#%*()_-+=")

Front 682

What params does errors.add take?

Back 682

two
first - :attr_name
second - msg

Front 683

How to see the errors on a particular attribute

Back 683

person.errors.on(:name) # => "cannot contain the characters !@#%*()_-+="

Front 684

How to see the errors on a particular attribute as seen in the form displayed to a user (ie. attr name appeneded)

Back 684

person.errors.full_messages # => ["Name cannot contain the characters !@#%*()_-+="]

Front 685

person.errors.on(:name) returns what if there are no errors?

Back 685

nil

Front 686

person.errors.on(:name) returns what if there are multiple errors?

Back 686

an array of errors

Front 687

How do you intentionally want to clear all the messages in the errors collection.

Back 687

person.errors.clear

Front 688

calling errors.clear upon an invalid object won’t .....

Back 688

actually make it valid: the errors collection will now be empty, but the next time you call valid? or any method that tries to save this object to the database, the validations will run again

Front 689

returns the total number of error messages for the object.

Back 689

person.errors.size # => 3

Front 690

What are callbacks

Back 690

methods that get called at certain moments of an object’s lifecycl

Front 691

what are the two ways to register callbacks

Back 691

before_validation :ensure_login_has_a_value
#where there is a private method with this name

before_create {|user| user.name = user.login.capitalize if user.name.blank?}
#use a block for one liners

Front 692

callback before save

Back 692

before_save

Front 693

callback after save

Back 693

after_save

Front 694

callback after update

Back 694

after_update

Front 695

callback before update

Back 695

before_update

Front 696

callback before destroying an object

Back 696

before_destroy

Front 697

callback after destroying an object

Back 697

after_destroy

Front 698

callback before validations

Back 698

before_validation

Front 699

Callback will be called whenever an Active Record object is instantiated, either by directly using new or when a record is loaded from the database.

Back 699

after_initialize

Front 700

callback will be called whenever Active Record loads a record from the database.

Back 700

after_find

Front 701

Note that after_initialize and after_find will both ....

Back 701

significantly slow down the queries as they will both be called for each record found in the database

Front 702

give examples of methods which trigger the after_find callback

Back 702

all, first, find find_by_attr, last

Front 703

what update action skips callbacks

Back 703

update_all

#note that update and update_attributes and update_attributes(!) all run callbacks

Front 704

what delete action skips callbacks

Back 704

# delete
# delete_all

#note that destroy, destroy_all all run callbacks

Front 705

what is the execution chain?

Back 705

all your model’s validations, the registered callbacks, and the database operation to be executed.

Front 706

If any before callback method returns exactly false or raises an exception

Back 706

the execution chain gets halted and a ROLLBACK is issued

Front 707

What happens if you have an after destroy method in posts and destroy a user (which has many dependent =>destroy posts)

Back 707

the after_destroy in the post method is called

Front 708

how to make the running of callbacks conditional?

Back 708

using the :if and :unless options, which can take a symbol, a string or a Proc

#just like validations

Front 709

give an example of a before_save callback conditional on a proc which requires order be paid by hard

Back 709

before_save :normalize_card_number, :if => Proc.new { |order| order.paid_with_card? } end

Front 710

When writing conditional callbacks, it’s possible to mix

Back 710

both :if and :unless in the same callback declaration.

after_create :send_email_to_author, :if => :author_wants_emails?, :unless => Proc.new { |comment| comment.post.ignore_comments? }

Front 711

If callback methods that you’ll write will be useful enough to be reused by other models how do you do so?

Back 711

#create a class ModelCallbacks
# def the callbacks (may take the object as a param)
#call the ModelCallback.new in the callback register

class PictureFileCallbacks
def after_destroy(picture_file)
File.delete(picture_file.filepath) if
File.exists?(picture_file.filepath) end
end

#in PictureFile class
after_destroy PictureFileCallbacks.new

Front 712

why use observers instead of callbacks?

Back 712

allow you to add the same functionality outside of a model. For example, it could be argued that a User model should not include code to send registration confirmation emails.

Front 713

magine a User model where we want to send an email every time a new user is created. Because sending emails is not directly related to our model’s purpose, we could create an observer to contain this functionality.

Back 713

class UserObserver < ActiveRecord::Observer

def after_create(model)
# code to send confirmation email... end
end

Front 714

Where are Observers are conventionally placed .....

Back 714

app/models directory

Front 715

for observers to work what else must be done

Back 715

they must be egistered in your application’s config/environment.rb file

config.active_record.observers = :user_observer

Front 716

How can single observers be used to add behaviour to more than one model

Back 716

class MailerObserver < ActiveRecord::Observer

observe :registration, :user

#note that this observe macro style method is not necessary if only one model is being observed as Rails will strip the model from the class name

Front 717

should controllers have singular or plural names?

Back 717

plural

emails_controller
#not email_controller

Front 718

How to format a date object in a Rails view?

Back 718

.strftime('%B %Y')

#%B = month
%Y = year

Front 719

Action Pack is single gem which contains ....

Back 719

Action Controller, Action View and Action Dispatch. The “VC” part of “MVC”.

Front 720

Services provided by Action Controller include ....

Back 720

session management, template rendering, and redirect management.

Front 721

Action View manages ...

Back 721

rendering templates, including nested and partial templates, and includes built-in AJAX support.

Front 722

Action Dispatch handles routing of ....

Back 722

web requests and dispatches them as you want, either to your application or any other Rack application

Front 723

Active Model provides a ..

Back 723

defined interface between the Action Pack gem services and Object Relationship Mapping gems such as Active Record

...allows Rails to utilize other ORM frameworks in place of Active Record if your application needs this.

Front 724

Active Record is ...

Back 724

provides database independence, basic CRUD functionality, advanced finding capabilities, and the ability to relate models to one another, among other services.

Front 725

Active Resource provides ....

Back 725

a framework for managing the connection between business objects and RESTful web service

map web-based resources to local objects with CRUD semantics.

Front 726

Active Support is a ...

Back 726

collection of utility classes and standard Ruby library extensions that are used in the Rails, both by the core code and by your applications.

Front 727

Railties is

Back 727

code that builds new Rails applications and glues the various frameworks and plugins together in any Rails application.

Front 728

how to install Rails

Back 728

gem install rails
#through rubygems

Front 729

HOw to start a Rails application called blog?

Back 729

$ rails new blog

Front 730

Action Controller ....

Back 730

processes incoming requests to a Rails application, extracts parameters, and dispatches them to the intended action.

Front 731

In what file do you tell others what your application does, how to set it up, and so on.

Back 731

README.rdoc

Front 732

how to install all gems on a new application

Back 732

bundle install

Front 733

how to create a db with Rails

Back 733

$ rake db:create

Front 734

when you run rails server where will you see your app running in the browser?

Back 734

http://localhost:3000.

Front 735

how to run a migration

Back 735

$ rake db:migrate

Front 736

why do migration files include timestamps?

Back 736

to ensure that they’re processed in the order that they were created.

Front 737

Models inherit from what class?

Back 737

ActiveRecord::Base

#gives it basic database CRUD (Create, Read, Update, Destroy) operations, data validation, as well as sophisticated search support and the ability to relate multiple models to one another.

Front 738

Migrations inherit from what class?

Back 738

ActiveRecord::Migration

Front 739

How to create a Post with content attr "A New Post!"

Back 739

Post.create(:content => "A new post")

Front 740

diff between console and develpoemnt web server

Back 740

console does not automatically load your code afresh for each line. If you make changes to your models while the console is open, type reload! at the console prompt to load them

Front 741

Rails 3 auto escapes HTML - how to get unescaped stuff?

Back 741

<%= raw post.name %>.

Front 742

how to call a form partial from within a new view file (@post defined)

Back 742

<%= render 'form' %>

#@post can be used in the partial now since partials receives all the instance variables defined in the calling view file,

Front 743

how to instantiate a new Post object from the data supplied by the user on the form, which Rails makes available in the params hash.

Back 743

Post.new(params[:post])

Front 744

how to redirect to showing an indiv post

Back 744

redirect_to(@post)

Front 745

how to re-render the new action

Back 745

render :action => "new"

Front 746

how to find an individual post for showing or editing

posts/1

Back 746

@post = Post.find(params[:id])

Front 747

how to update a post with supplied params attributes

Back 747

@post.update_attributes(params[:post])

Front 748

to where should you redirect after @post.destroy in a controller destroy action

Back 748

the index since there isn't any record to display

redirect_to(posts_url)

Front 749

what sets up a foreign key column for the association between the two model

Back 749

other_model:references

#in migration t.references :other_model

Front 750

what appears in the model which has the foreign_key column

Back 750

belongs_to :post

Front 751

in routes how do you capturing the hierarchical relationship that exists between posts and comments.

Back 751

resources :posts do
resources :comments
end

Front 752

What do most controllers inherit from?

Back 752

ApplicationController

Front 753

how to create comments on a post variable (in the comments controller)

Back 753

#find the relevant post, call its comments, and call c reate on that using the params hash - will auto link the comment so it belongs to a particular post

@post = Post.find(params[:post_id])
@comment = @post.comments.create(params[:comment])

Front 754

what will the form for a post's comment look like

Back 754

#in a post show file - not the array in the form_for with the post var and the building of comments

<%= form_for([@post, @post.comments.build]) do |f| %>

Front 755

how to render a collection of partials for all the comments associated with a given post

Back 755

<%= render :partial => "comments/comment", :collection => @post.comments %>

Front 756

ou delete a post then it’s associated comments will also need to be deleted - how to do this

Back 756

#WiTHIN the posts file

has_many :comments, :dependent => :destroy

#put dependent=> destroy in the declaration of the association with the other model (

Front 757

How to assign a section in database.yml file to a variable (details)

Back 757

# &variable_name straight after server type declaration

development: &details
database: sql
etc.
production:
....

Front 758

How to reuse a variable in a section in database.yml (details)

Back 758

# <<: *variablename under the inheriting server type declaration

production:
<<: *details

Front 759

how to avoid a NoMethodError in a view
e.g. age of a person variable

Back 759

@person.try(:age)

Front 760

when you are generating a model which has another models foreign key what do you say

Back 760

#other_model_name(singular):references

r g model tag post:references

Front 761

how to accept attributes for another model (e.g. tags) from within a post form (code thats needed in the model)

Back 761

accepts_nested_attributes_for :tags

Front 762

in a post model which accepts nested attributes for tags how to prevents saving new tags that do not have any attributes filled in.

Back 762

#pass a reject_if option with a proc looking at whether the attributes are black

accepts_nested_attributes_for :tags, :reject_if => proc { |attrs| attrs.all? { |k, v| v.blank? } }

Front 763

how to ensure there is a tag object ready on a post form (for nested attributes)

Back 763

@post.tags.build

Front 764

view helpers provide ...

Back 764

small snippets of reusable code for views

Front 765

what comes at the top of a helper (e.g. posts_helper)

Back 765

module PostsHelper

#so its a module not a class

Front 766

give an example of a helper which accepts a post object

how do you call it

Back 766

def join_tags(post)
post.tags.map { |t| t.name }.join(", ") end

#call with
<%= join_tags(@post) %>

Front 767

. The application object (which every Rails 3 app must have) is defined in ...

Back 767

config/application.rb

#contains lots of old environment.rb stuff

Front 768

what plugin automates part of the Rails 3 upgrade process

Back 768

Rails Upgrade - call rails:upgrade:check to run (can generate Gemfile)

Front 769

how to start a Rails 3 application (given that they have their own name space)

Back 769

YourAppName.boot

Front 770

entral repository of all sorts of Rails wide configuration options.

Back 770

Rails.config object

Front 771

what has been added to the Root path

Back 771

Rails.root/app

Front 772

Rails Generators API was merged with what ...

Back 772

Rails templates API

Front 773

where to place files to override templates in generators

Back 773

Rails.root/lib/templates.

Front 774

view the routes for one controller.

Back 774

rake routes CONTROLLER=x

Front 775

RAILS_ENV is now

Back 775

Rails.env

Front 776

RAILS_ROOT is now

Back 776

Rails.root

Front 777

is protect_from_forgery on or off by default in Rails 3

Back 777

protect_from_forgery is on by default (in application_controller.rb)

Front 778

defaults for session store are stored where?

Back 778

config/initializers/session_store.r

Front 779

How to set encrypted values in cookies

Back 779

cookie.secure[:key] => value.

Front 780

# Instead of: ActionController::Routing::Routes.draw do |map| map.resources :posts end

# You do:

Back 780

AppName::Application.routes do resources :posts end

#notes
# 1 AppName namespacing
# 2 lack of map - just put resources

Front 781

Rails router is now ...

Back 781

rack_mount with a Rails DSL

Front 782

how to make a form use AJAX

Back 782

form_for @post, :remote => true

Front 783

form_for is called in what different way now?

Back 783

<%= form_for @post do |f| %>

#needs <%= instead of just <%

Front 784

what awesome new attribute based validation shortcut method does Rails 3 introduce?

Back 784

validates :attribute, options_hash

Front 785

how are options such as presence, uniquenss and acceptance used in the

validates :attribute, options_hash shortcut

Back 785

# :presence => Boolean.

Front 786

how are options such as exclusion and inclusion used in the

validates :attribute, options_hash shortcut

Back 786

# :exclusion => { :in => Ennumerable }.
# :inclusion => { :in => Ennumerable }.

#note the subhash using :in

Front 787

What filename does bundler use?

Back 787

Gemfile

Front 788

how to add a gem to your app in the gemfile (basic formula with version)

Back 788

gem "gem_name", "version"
gem "haml", "1.8.6"

#notice the quotes around gem version

Front 789

how to specify a gem should be greater than a certain version

Back 789

gem "haml", "> 1.8.6"

Front 790

how to specify a gem should have a dif name than defaul in require_env call

Back 790

gem "name", "version", :require_as =>"file"
gem "sqlite3", "13". :require => "sq-slite"

Front 791

how to specify where in git a gem is to be found

Back 791

gem "name", "version", :git => "git://github.com/wycats/thor":

Front 792

how to specify a gem should only run in certain environments

Back 792

e.g. group :development do
gem "rails"
end

#only block

#use only

Front 793

how to specify an original gem only runs in production

Back 793

gem "foo", :group => :production

#contrast this to the block group method

Front 794

how to install gems using bundler

Back 794

bundle install

Front 795

what does bundle lock do

Back 795

When you're ready to share your application or deploy it, lock down all the versions of the gems you're using so there is no inconsistencies on deploy

Front 796

how to use a gem you are actively developing on your machine?

Back 796

gem "nokogiri", :path => "~/Code/nokogiri"

#specify the path variable

Front 797

how to install all dependencies expect those in specified groups

Back 797

$ bundle install --without test

Front 798

how to specify a gem should use a particular branch on git

Back 798

gem "rails", :git => "git://github.com/rails/rails.git", :branch => "2-3-stable"

Front 799

.bundle folder is ..

Back 799

specific to each machine -- thus should be gitignored

Front 800

how to specify a gem dependency in multiple groups

Back 800

ou can place a dependency in multiple groups at once as well

group :development, :test do
gem "wirble"
gem "ruby-debug"
end

Front 801

After locking your dependencies you may not modify the Gemfile without unlocking first - what do you type?

Back 801

bundle unlock

Front 802

how to save without validating (previously save(false))

Back 802

save(:validate => false)

Front 803

scope whereby you check for models created later than a certain (variable) date

Back 803

scope :since, lambda {|time| where(“created_at > ?”, time)

Front 804

what function is used to format date and time in ruby?

Back 804

strftime function

Time.now().strftime(“%d/%m/%y %H:%M”)

Front 805

what strftime option (placed inside the quotes insides the bracketed params to the function) gives you:

August

Back 805

%B

Front 806

what strftime option (placed inside the quotes insides the bracketed params to the function) gives you:

20 (date)

Back 806

%e

Front 807

what strftime option (placed inside the quotes insides the bracketed params to the function) gives you:

2008

Back 807

%Y

Front 808

what strftime option (placed inside the quotes insides the bracketed params to the function) gives you:

Aug

Back 808

%b

Front 809

what strftime option (placed inside the quotes insides the bracketed params to the function) gives you:

08 (month)

Back 809

%m

Front 810

what strftime option (placed inside the quotes insides the bracketed params to the function) gives you:

16 (hours on 24 clcok)

Back 810

%H

Front 811

what strftime option (placed inside the quotes insides the bracketed params to the function) gives you:

56(minutes)

Back 811

%M

Front 812

what strftime option (placed inside the quotes insides the bracketed params to the function) gives you:

21 (seconds)

Back 812

%S

Front 813

what strftime option (placed inside the quotes insides the bracketed params to the function) gives you:

11 (hour of day on 12 hour clock

Back 813

%I

Front 814

what strftime option (placed inside the quotes insides the bracketed params to the function) gives you:

am / pm

Back 814

%p

Front 815

what strftime option (placed inside the quotes insides the bracketed params to the function) gives you:

Sun (abbreviated weekday name)

Back 815

%a

Front 816

what strftime option (placed inside the quotes insides the bracketed params to the function) gives you:

Sunday (full weekday name)

Back 816

%A

Front 817

what strftime option (placed inside the quotes insides the bracketed params to the function) gives you:

GMT (time zone name)

Back 817

%Z

Front 818

what strftime option (placed inside the quotes insides the bracketed params to the function) gives you:

98 (year without the century)

Back 818

%y

Front 819

Time.now - 10 gives what

Back 819

10 seconds ago

#simple arithmetic is in seconds with time objects

Front 820

what's the date equivalent of Time.now

Back 820

Date.today

Front 821

Date.today + 1 gives what

Back 821

1 day later

#simple arithmetic is in days with date objects

Front 822

how to create a table in a migrtion

Back 822

def self.up
create_table :products do |t|
t.

Front 823

what col comes for free in migrations

Back 823

primary key

Front 824

how to fix bad data in a migration

Back 824

User.update_all ["receive_newsletter = ?", true]

#done outside / after the change_table part but before self.up has ended

Front 825

how are migration files named

Back 825

YYYYMMDDHHMMSS_create_products.rb, that is to say a UTC timestamp identifying the migration followed by an underscore followed by the name of the migration

Front 826

what naming convention must you remember with migrations

Back 826

The name of the migration class (CamelCased version) should match the latter part of the file name.

0080906120000_create_products.rb should define CreateProducts

Front 827

what to do if you messed up your previous migration (if migration only run on dev machine)

Back 827

rollback the migration (for example with rake db:rollback), edit your migration and then run rake db:migrate to run the corrected version.

Front 828

what to do if you messed up your previous migration (if migration run on production)

Back 828

write a new migration that performs the changes you require.

Front 829

default format of rails model generator cmd

Back 829

rails generate model Product name:string description:text

#model name is capitalized
#name of column comes before data type

Front 830

what special cmd line format creates a migration containing the appropriate add_column and remove_column statements will be created.

Back 830

“AddXXXToYYY” or “RemoveXXXFromYYY” and is followed by a list of column names and type

rails generate migration AddPartNumberToProducts part_number:string

Front 831

if you don’t want a primary key at all (for example for a HABTM join table) you can pass

Back 831

:id => false

create_table firm_solicitors, :id => false do |t|

Front 832

what close cousing of create_table is used to change_tables

Back 832

change_table :products do |t|
t.remove :description, :name
end

Front 833

how to add a string column within a change_table blcok

Back 833

t.string :part_number

#same as create table syntax

Front 834

how to rename a column in a change table block

Back 834

t.rename :upccode, :upc_code

Front 835

how to create a category_id column of the appropriate type on the products table

Back 835

create_table :products do |t|
t.references :category
end

#Note that you pass the model name, not the column name.

Front 836

how to output code in a model to the log?

Back 836

logger.debug "#{@months_histogram.values.inspect}"

Front 837

how to create an attachment_id col and a attachment_type column with a default of 'photo'

Back 837

t.references :attachment, :polymorphic => {:default => 'Photo'}

Front 838

how to run sql commands from a migration

Back 838

#being with execute <<-SQL
# end with SQL

execute <<-SQL ALTER TABLE products ADD CONSTRAINT fk_products_categories FOREIGN KEY (category_id) REFERENCES categories(id)
SQL

Front 839

what does the error IrreversibleMigration mean

Back 839

raised when you are trying to run a down migration but you can' t reverse a migration - e.g. destroyed data

Front 840

db:migrate does what

Back 840

runs the up for all migrations not yet run

Front 841

running the db:migrate also invokes the

Back 841

db:schema:dump task,

Front 842

db:schema:dump task doew what

Back 842

update your db/schema.rb file to match the structure of your database.

Front 843

to migrate to version 20080906120000 run

Back 843

rake db:migrate VERSION=20080906120000

Front 844

go to previous migration

Back 844

rake db:rollback

Front 845

go back 3 migrations

Back 845

rake db:rollback STEP=3

#step param with rollback
#note that params are capitalized and use equals signs

Front 846

doing a rollback and then migrating back up again.

Back 846

db:migrate:redo

Front 847

drop the database, recreate it and load the current schema into it.

Back 847

db:reset

Front 848

If you need to run a SINGLE specific migration up or down

Back 848

db:migrate:up and db:migrate:down

#Just specify the appropriate version

rake db:migrate:up VERSION=20080906120000

Front 849

within a migrate up or down how do you get terminal outpu of "created a table lol!"

Back 849

say "Created a table lol"

Front 850

suppresses any output messages generated by its block in migrations

Back 850

#run the methods in a suppress_messages blcok

suppress_messages do
create_table :products do |t|
t.string :name
end

Front 851

If you just want Active Record to shut up when running migrations ...

Back 851

rake db:migrate VERBOSE=false

Front 852

If you add a column to a table in a migration and then try and use the corresponding model to insert a new row it may try to use the old column information - due to caching info about cols of a model.

How to get past this (w/in migration)

Back 852

#Model.reset_column_information

add_column :product, :part_number, :string
Product.reset_column_information

Front 853

Migrations, mighty as they may be, are not the authoritative source for your database schema..... what is?

Back 853

db/schema.rb

#not designed to be edited

Front 854

There is no need (and it is error prone) to deploy a new instance of an app by replaying the entire migration history. It is much simpler and faster to ...

Back 854

ust load into the database a description of the current schema.

Front 855

How to change the schema format setting

Back 855

#environment.rb file

config.active_record.schema_format

:sql or :ruby.

Front 856

When should you set the schema format to :sql.

Back 856

db/schema.rb cannot express database specific items such as foreign key constraints, triggers or stored procedures. While in a migration you can execute custom SQL statements, the schema dumper cannot reconstitute those statements from the database. If you are using features like this

Front 857

The Active Record way claims that intelligence belongs in your ..... not in your ........

Back 857

modesl - not the database

As such, features such as triggers or foreign key constraints, which push some of that intelligence back into the database, are not heavily used.

Front 858

In a view how do you get a yaml form of an object

Back 858

#pass debug then the object

<%= debug @post %>

Front 859

In a view how do you get a yaml form of an instance var, method or object

Back 859

# to_yaml

<%= @post.to_yaml %>

Front 860

when working with arrays or hashes how do you view somethig (for debugging) in a view

Back 860

#inspect

<%= [1, 2, 3, 4, 5].inspect %>

Front 861

activate Rails built-in support to debug RJS,

Back 861

in the Rails::Initializer do |config| block inside environment.rb:


config.action_view[:debug_rjs] = true

Front 862

How many log files does Rails use?

Back 862

Rails maintains a separate log file for each runtime environment.

Front 863

HOw to specify an alternative logger (eg. Log4R)

Back 863

#in any environment file

ActiveRecord::Base.logger = Log4r::Logger.new("Application Log")

# In any initialzier
config.logger = Log4r::Logger.new("Application Log")

Front 864

default log file name is ...

Back 864

environment_name.log.

Front 865

see current log level

Back 865

ActiveRecord::Base.logger.level

Front 866

What log levels are available?

Back 866

:debug, :info, :warn, :error, and :fatal

Front 867

How to change the default log level, use

Back 867

# In any environment initializer

#look how you use the Logger::LEVEL syntax (following a config.log_level)

config.log_level = Logger::WARN

Front 868

default Rails log level in production

Back 868

info [1]

Front 869

default Rails log level in test / dev

Back 869

test [0]

Front 870

To write in the current log ....

Back 870

use the logger.(debug|info|warn|error|fatal) method from within a controller, model or mailer

logger.debug "Person attributes hash: #{@person.attributes.inspect}"

Front 871

住民

Back 871

주민
residents, inhabitants [reside + people]

Front 872

The debugger used by Rails, ruby-debug, comes

Back 872

as a gem

gem install ruby-debug

Front 873

nside any Rails application you can invoke the debugger by calling the ...

Back 873

debugger method.

def new
debugger
@person = Person.new
end

Front 874

what does this message in the logs mean?

***** Debugger requested, but was not available: Start server with --debugger to enable *****

Back 874

you need to restart the server with script/server --debugger

Front 875

As soon as your application calls the debugger method ...

Back 875

e debugger will be started in a debugger shell inside the terminal window where you launched your application server, and you will be placed at ruby-debug’s prompt (rdb:n).

Front 876

how to get info about available commands in debug mode?

Back 876

help

or help command

Front 877

how to abbreviate ruby-debug commands

Back 877

by supplying just enough letters to distinguish them from other commands, so you can also use l for the list command.

Front 878

list in rdb does what?

Back 878

shows you where you are in the code by printing 10 lines centered around the current line; the current line in this particular case is line 6 and is marked by =>.

Front 879

what happens if you press l again whilst already in list

Back 879

the next ten lines of the file will be printed out. - 10 more again, eventually going back up to the beginning of the file

Front 880

print the backtrace of the application in rdb mode?

Back 880

backtrace

or where

Front 881

how to move anywhere you want in a rdb backtrace

Back 881

frame n

#where n is a number, the frame of the backtrace

Front 882

how to move up and down a backtrace

Back 882

up n
down n

Front 883

in rdb how do you evaluate something in the current context.

Back 883

just type it!

#@posts = Post.find(:all)

Front 884

how to get all the instance variables within a context in rdb

Back 884

type
instance_variables

#dynamically updated as you execute code

Front 885

test if an instance variable (@ posts) is available within the current context of code in rdb

Back 885

instance_variables.include? "@posts"

Front 886

vost convenient way to show variables and their values:

Back 886

var

Front 887

show global vars in rdb

Back 887

var global
v g

Front 888

show local vars in rdb

Back 888

var local
v l

Front 889

show instance variables of object in rdb

Back 889

v[ar] i[nstance] <object>

#e.g. var instance Post.new

Front 890

way of tracking the values of a variable while the execution goes on in rdb

Back 890

display @recent_comments

The variables inside the displaying list will be printed with their values after you move in the stack

Front 891

如前

Back 891

여전
remain unchanged, be as before, be as (it) used to be, be just as it was. [like, as if + before]

Front 892

continue running your program until the next logical stopping point and return control to ruby-debug.

Back 892

step

or next

Front 893

to move forward n steps respectively in rdb

Back 893

step n

Front 894

火力

Back 894

화력
caloric (force), heating power, thermal power [fire + power]

Front 895

how to look at a new post in debugger

Back 895

var instance Post.new

Front 896

what does a breakpoint do?

Back 896

makes your application stop whenever a certain point in the program is reached

Front 897

add breakpoints dynamically with the command

Back 897

break (or just b)

Front 898

set breakpoint in the line in the current source file.

Back 898

break line
e.g.
break 10

Front 899

command to disable breakpoints (in rdb)

Back 899

disable breakpoint

Front 900

list breakpoints.

Back 900

info breakpoints

Front 901

To delete breakpoints

Back 901

delete _n_ t

Front 902

intercept an exception of type exception-name when there would otherwise be is no handler for it.

Back 902

catch exception-name
(or just cat exception-name)

Front 903

command in rdb to list all active catch points

Back 903

catch

Front 904

resume execution of an application that is stopped in the debugger:

Back 904

continue (or c)
finish (or f)

Front 905

edit file using the editor specified by the EDITOR environment variable. A specific line can also be given.

Back 905

edit [file:line]

Front 906

open the current file in TextMate

Back 906

tmate _n_ (abbreviated tm)

Front 907

exit the debugger

Back 907

quit command (q) or exit

Front 908

see full list of options in ruby debugger

Back 908

help set

Front 909

option to reload source code when changed in ruby debug

Back 909

set reload

Front 910

what are memory leaks in a rails app

Back 910

If a Ruby object does not go out of scope, the Ruby Garbage Collector won’t sweep it since it is referenced somewhere - eventually ***** up performance

Front 911

library for finding memory leaks in rails

Back 911

bleak_house (gem)

Front 912

how to set up your app for memory leak profiling

Back 912

# at the bottom of config/environment.rb:


require 'bleak_house' if ENV['BLEAK_HOUSE']

Front 913

how to start a server in bleak house mode

Back 913

RAILS_ENV=production BLEAK_HOUSE=1 ruby-bleak-house rails server

Front 914

how many requests should you make to get bleak house a good data sample

Back 914

couple hundred requests

Front 915

how to stop Bleak House and produce a dumpfile in /tmp:

Back 915

ctrl c

Front 916

what will the bleak house dumpfile show?

Back 916

your 20 leakiest lines of code

Front 917

code for creating a new order for a particular customer (both separate models w/ association)

Back 917

@order = @customer.orders.create(:order_date => Time.now)

#notice 1 - customer.orders (plural) calls create
# notice 2 create takes as params the attributes of the model being created)

Front 918

how to require that a customer model destroy all it's related order models when customer.destroy is called

Back 918

has_many :orders, :dependent => :destroy

Front 919

class Order < ActiveRecord::Base belongs_to :customer
end

what model has a foreign_id column?

Back 919

order -> since it must have a way of referencing the model it "belongs to"

Front 920

class Order < ActiveRecord::Base belongs_to :customer
end

what will the foreign_id col be called

Back 920

customer_id

Front 921

class Supplier < ActiveRecord::Base has_one :account
end

what model has a foreign_id column?

Back 921

account ->

#note that this is the opposite to the belongs_to

Front 922

when should you use a has_one relationship?

Back 922

If A has_one B, then when you create a new A you're probably going to be creating a new B as well.

Front 923

class Customer <ActiveRecord::Base
has_many :orders
end

where does the foreign_id column reside

Back 923

orders table -> since many different orders will point to the same customer

Front 924

How set up a many-to-many connection between Pysicians and Patients (using appointments)

Back 924

Physicians - hm apps(connecting table), hm patients, :through => apts (connecting table

Appointments - bt physicians, bt patients (bt both tables it connects)

Patients (as per physicians) - makes sense since both are equals on opposite sides of the hm_t table

Front 925

Code to set up a many-to-many connection between Pysicians and Patients (using appointments)

Back 925

class Physician < ActiveRecord::Base
has_many :appointments has_many :patients, :through => :appointments
end

class Appointment < ActiveRecord::Base
belongs_to :physician
belongs_to :patient
end

class Patient < ActiveRecord::Base has_many :appointments has_many :physicians, :through => :appointments
end

Front 926

using a hm through connection with physicians and patients (through appointments) how do you access a physicians pateints

Back 926

physician.patients

Front 927

association which indicates that the declaring model can be matched with ONE instance of another model by proceeding through a third model

Back 927

has_one :throug

Front 928

code for a has_one :through association

Back 928

#one side has_one of the other and has_one through tht connector, the other belongs_to the first, and has one connector, the connector table belongs to the second

class Supplier < ActiveRecord::Base has_one :account
has_one :account_history, :through => :account
end

class Account <ActiveRecord::Base
belongs_to :supplier
has_one :account_history
end

class AccountHistory < ActiveRecord::Base
belongs_to :account
end

Front 929

has_and_belongs_to_many usages in models

Back 929

declare the same in both models

class Assembly < ActiveRecord::Base has_and_belongs_to_many :parts end

class Part < ActiveRecord::Base has_and_belongs_to_many :assemblies
end

Front 930

creates a direct many-to-many connection with another model, with no intervening model

Back 930

has_and_belongs_to_many

Front 931

has_and_belongs_to_many in two models needs how many tables

Back 931

3 tables - a connecting one is needed despite having no mention in AR (i..e. no model file inheriting from AR)

[make sure to add the joining table in the migrations]

Front 932

you have a Assembly and a Part class which has_and_belong_to - what is the intervening table called

Back 932

assemblies_parts

#lower case plural first table _ lower case plural second table

Front 933

how to choose Between belongs_to and has_one

Back 933

semantic sense. For example, it makes more sense to say that a supplier owns an account than that an account owns a supplier.

Front 934

how to choose between has_many :through and has_and_belongs_to_many?

Back 934

you should set up a has_many :through relationship if you need to work with the relationship model as an independent entity. If you don’t need to do anything with the relationship model, it may be simpler to set up a has_and_belongs_to_many relationship

Front 935

how to make a model have a relation to itself? i.e. manager and subordinate employees

Back 935

#has_many :whatever_you_want, :class_name => "Same as file", :foreign_key => same_integer_column_in_the_table

class Employee
has_many :subordinates, :class_name => "Employee", :foreign_key => "manager_id"

belongs_to :manager, :class_name => "Employee" end

Front 936

psudeo code for a picture model that belongs to either an employee model or a product model using polymorphic

Back 936

picture model -> :bt => special_poly_name, :polymorphic => true

other models -> hm => pictures (original model), :as => :special_polymorphic_name

Front 937

code for a picture model that belongs to either an employee model or a product model using polymorphic

Back 937

class Picture
belongs_to :imageable, :polymorphic => true
end

class Employee
has_many :pictures, :as => :imageable
end

class Product
has_many :pictures, :as => :imageable
end

Front 938

if an employee has many picures using polymorphism what code retreives this set

class Employee
has_many :pictures, :as => :imageable
end

Back 938

@employee.pictures

Front 939

if an employee has many picures using polymorphism what code finds the parent of the given pic (employee / product)

class Employee
has_many :pictures, :as => :imageable
end

Back 939

@picture.imageable

Front 940

to make polymorphism work what do you need in the migrations

Back 940

you need to declare both a foreign key column and a type column in the model that declares the polymorphic interface

so if pictures has polymorphic => true (as imageable) then migration needs these extra columns

t.integer :imageable_id t.string :imageable_type

Front 941

All of the association methods are built around .... which means ....

Back 941

caching / the result of the most recent query available for further operations

customer.orders
# retrieves orders from the
database
customer.orders.size # uses the cached copy of orders customer :-)

Front 942

if you are using assocation methods and you want to reload the cache, because data might have been changed by some other part of the application? Just

Back 942

Just pass true to the association call:

customer.orders(true).empty?

Front 943

For belongs_to associations you need to create what in your db / migrations?

Back 943

foreign keys,

Front 944

For has_and_belongs_to_many associations you need to create what in your db / migrations?

Back 944

you need to explicitly create the joining table with integer columns of the model_id of each of the two habtm -

primary key should be turned off too
create_table :assemblies_parts, :id => false do |t|

Front 945

how to specify a different join table name than the AR default (

Back 945

:join_table option,

Front 946

how does AR make the join table

Back 946

plural of the tables, in lexical order (c before f - although weird stuff can happen as it uses > string ) separated with an underscore

Front 947

By default, associations look for objects only within the ....

Back 947

current module’s scope

#here both classes are w/in the business module so can access each other directrly.
module Business
class Supplier < ActiveRecord::Base
has_one :account end

class Account < ActiveRecord::Base belongs_to :supplier
end
end

Front 948

If a class is declared in a module Biz who do you access it

Back 948

Biz::class-name

thus for the association to work you must declare the class name with the module name space

has_one :account, :class_name => "Biz::Account"