Ruby Sass

Front 1

?

Back 1

conventional in Ruby to have '?' at the end of the method if that method returns only boolean values

Front 2

@

Back 2

instance variable

Front 3

lambda

Back 3

lambda is just a function... peculiarly... without a name. They're anonymous, little functional spies sneaking into the rest of your code. Lambdas in Ruby are also objects, just like everything else!

Hint 3

convention is to use {} for single line lambdas and do..end for lambdas that are longer than a single line.

Front 4

Lambdas vs. Blocks

Back 4

A lambda is a piece of code that you can store in a variable, and is an object. The simplest explanation for a block is that it is a piece of code that can't be stored in a variable and isn't an object. It is, as a consequence, significantly faster than a lambda, but not as versatile and also one of the rare instances where Ruby's "everything is an object" rule is broken.

Front 5

most common uses for a lambda

Back 5

one of the most common uses for a lambda involves passing exactly one block to a method which in turn uses it to get some work done. You'll see this all over the place in Ruby - Array iteration is an excellent example.

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module

Back 6

Modules only hold behaviour, unlike classes, which hold both behaviour and state.

Since a module cannot be instantiated, there is no way for its methods to be called directly. Instead, it should be included in another class, which makes its methods available for use in instances of that class.

Front 7

::

Back 7

:: is a constant lookup operator that looks up the Array constant only in the Perimeter module.

Front 8

symbol, ex :octocat

Back 8

immutable string whose value is itself, typically used for enumeration. its own primitive type

Hint 8

used in Ruby to denote "specialness" such as being one of the set of fixed choices like an enumeration. Symbols can easily be converted back and forth with the methods to_s and to_sym.

Front 9

return value of puts versus return value of addion

Back 9

always nil versus sum

Hint 9

1+1 returns 2

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primitives versus objects

Back 10

primitives dont have a common relationship to each other

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variables

Back 11

will always be undefined or ACT like an object

Hint 11

they are not objects

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variable scope indicators

Back 12

Global $variable
Class @@variable
Instance @variable
Local variable
Block variable

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array

Back 13

An array is an ordered integer- indexed collection of objects.
That's a very fancy way of saying that we can take objects and put them together in order, and keep their position in the same order, and we can refer to those objects by their positions.

Hint 13

Expanding file folder is good analogy because folders can be empty. Classes can be put in arrays, expa

Front 14

a.b means: ____ ____ b on ______ a

Back 14

•a.b means: call method b on object a
•a is the receiver to which you send the method call,
assuming a will respond to that method
•does not mean: b is an instance variable of a
•does not mean: a is some kind of data structure
that has b as a member

Front 15

def by_three?

Back 15

best practice to end methods with a question mark if they return a boolean in ruby

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blocks

Back 16

create a method with no name. Blocks can be defined with either the keywords do and end or with curly braces ({}).

Front 17

is 0 true of false

Back 17

0 or empty string is true. False and nil are the only things that are true. They are not the same thing but they both return false

Front 18

what is returned by default from a method?

Back 18

- if a method does not explicitly return a value, the last expression’s value is returned, ex

Front 19

poetry mode

Back 19

omit paretheses around arguments to a method call, and omit curly braces when LAST argument to a method call is a hash

Hint 19

there's a single hash argument, and its the last argument