Ruby

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.strip

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function for String class to get rid of leading and trailing whitespace

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.split

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Divides an array into substrings based on a delimiter (commas, spaces)

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someArray(&:someMethod)

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calls to_proc to turn into:

something {|i| i.foo }

from

something(&:foo)

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difference between a module and a class?

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Modules are about creating functions and sharing them among multiple classes. Classes are about objects, modules are about methods.

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What is '==' in Ruby?

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Tests whether two things are equal in value. Tests equivalence

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What is equal?() in Ruby?

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Tests whether two objects are the same

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Difference between 'and' and '&&' in Ruby?

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'and' has a lower precedence than '='

'&&' has a higher precedence than '='

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What is the basic syntax for giving a variable 'x' a regular expression output?

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x = /someRegex/.match("some string")

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Ruby string interpolation, how can you use it and what does it look like?

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String interpolation is used with double quotes "", so for any number i, the syntax goes "#{i}"

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What is the name of any constructor in Ruby code?

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class someClass

initialize(someParameter)

end

end

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Difference between super and super() in Ruby?

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super calls the parent class with the same parameters pass in the child class, while super() calls the parent class with no parameters

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obj1.eql?(obj2)

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Checks whether the value and type of two operands are the same

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"someString".gsub(/pattern/, "x")

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returns a copy of the string where all occurrences of the pattern are replaced with 'x'

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Explain %() in ruby

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Creates a string within the parentheses

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::

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A way to access things in a class that are available at the class-level

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+= vs. .concat()

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+= reinitializes an object in ruby while .concat() merely concatenates what's in the parenthesis to the original object

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someObject.respond_to?("someMethod")

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checks whether or not an object has a specific method in it, including all the methods inherited by anscestors

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.include?() .includes()

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.include?() Ruby seems to take precedence in question marks...

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difference between .each(), .collect(), .map()?

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.each() returns the same array, while .collect() and .map() return new arrays

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.push() in ruby?

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Used for arrays

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Difference between:

class Dog1

def bark() { return "woof woof" }

end

and

class Dog2

def self.bark() { return "woof woof" }

end

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You'll have to instantiate an object in order to call on the first bark, while the second bark can be obtained at the class level:

fido = Dog1.new

puts fido.bark()

puts Dog2.bark()

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What does this do?

.any? do end

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it iterates over an array and will return true if the code block is ever true

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What does this do?

.select() do end

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iterates over an array and will return all the elements for which the code block is true

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What does this do?

.find() do end

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returns the first element in an array for which the code block returns true

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What does this do?

.find_index() do end

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returns the first index of an array for which the code block returns true

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.to_f

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turns an integer into a floating point number

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how do you inherit a module into a class?

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you put include somewhere in the class block

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.merge()

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merges two hashes together

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What is the access control of of protected methods in ruby?

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Protected methods can only be invoked by objects of the defining class and its subclasses.

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How do you turn any object into a constant in ruby?

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Object.freeze

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What does .allocate() do?

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If you have a class that has an initialize() function and you want to create an object but don't want to call its initialize

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regular expression modifier: i

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ignore case when matching text

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regular expression modifier: o

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perform #{} interpolation only once, the first time the regexp literal is evaluated

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regular expression modifier: x

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Ignores whitespace and allows comments in regular expressions

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regex modifier: m

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Matches multiple lines, recognizing newlines as normal characters

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u,e,s,n

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Interpret the regexp as Unicode (UTF-8), EUC, SJIS, or ASCII. If none of these modifiers is specified, the regular expression is assumed to use the source encoding.

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How do you get the index for each character in a string in ruby?

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each_char.with_index()

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DID YOU KNOW you can do string interpolation into regex?

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it looks like this. /#{someVariable}/

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As a safe bet, which variable number should index be for each_index() operators?

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the second one

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how do you remove a value from an array directly in ruby?

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someArray.delete(value)

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How do get the n min/max values from an array?

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someArray.min(n)

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Describe the four ways in which the reduce function in ruby can be used.

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reduce(initial, sym) → obj

reduce(sym) → obj

reduce(initial) { |memo, obj| block } → obj

reduce { |memo, obj| block } → obj

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What is the exact same as .reduce() in ruby?

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.inject()

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what is the return value of .inject() in ruby?

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the final value of memo

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What happens when you put a binary operation in .reduce()? (example: .reduce(:+))

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combines each of the values in array using the given binary operation

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describe the syntax for ruby's case operation

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case x

when (condition) ....

when(condition2).....

end

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explain the ruby function:

someString.tr(from_str, to_str)

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changes the characters in someString from the characters in from_string to to_string character by character

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What are the different ways to call Ruby methods?

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1.) Calling them directly using the dot operator

2.) Using the .send(:methodSym, params) method

3.) Instantiating the method object then using the .call() method. For example,

method_object = someObj.method(:someMethod)

method_object.call(optParams)

4.) Using the eval method:

eval "s.length"

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How can you call private methods in Ruby?

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class Flass

private

def hi

puts "hello world"

end

end

f = Flass.new

f.send :hi ## returns "hello world"

f.method(:hi).call ## returns "hello world"

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array1 - array2 = ?

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deletes item by item whatever's in array2 that is also in array1

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.delete_at()

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deletes the array item at that index

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.match() vs =~

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both return nil of there's no match

.match() returns matchData instance if there is a match and the other returns the numerical position where the match started

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someMatch.string, what does this return?

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it returns the original string matched

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someMatch.regexp, what does this return?

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it returns the regular expression used in the match

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someMatch[0], what does this return?

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the match between the string and the regexp for some .match() function

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someMatch[n], what signified the number of n in someMatch?

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the number of groupings used in the regular expression

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for regular expressions, what is the difference between .sub() and .gsub()?

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.sub() only changes the first match while .gsub() [think, global sub] changes all matches

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What is the backslash-number pattern in ruby regular expressions? (\someNumber)

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it is a variable holding one regular expression grouping

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What is $1...$n in terms of ruby regular expressoins?

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They are the global variables created denoting the grouping found for a regular expression match

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What is the purpose of the '!!' (double bang) sign in ruby?

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it is used for variables and transforms the variable to give its original boolean value in a boolean context. The first bang sign switches to variable to a boolean context, negates it, and the second bang sign negates that negation, resulting in the original boolean value for that variable in a boolean context

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What is the difference between 'require' and 'require_relative' in Ruby?

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With 'require', Ruby looks in the $LOAD_PATH global variable and checks if the file to require is there, while in 'require_relative', Ruby checks for the files relative to the file that you're in/requiring from.

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What is the difference between 'be_kind_of' and 'be_instance_of' in Ruby?

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be_instance_of returns true/false if the actual value is an instance of an expected class

be_kind_of returns true/false if the actual value is an instance of an expected class OR any of the class' parent classes

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What is double() in Rspec?

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Creates a mock of a dependency. it is the ruby version of mocking.

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how is stubbing done in rspec?

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through the allow() method with the syntax: allow(someClass).to receive(:someStub) { someValue }

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.uniq in ruby?

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removes all duplicates of items in an array

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How do you run specific tests in rspec from the command line?

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test_file.rb

it "do stuff", :customTag => true do

puts "runs when called"

end

command line:

rspec --tag customTag

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how does one get very descriptive, formatted rspec test results?

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rspec --format doc all_doc_names.rb