Quiz: Class Variables and Methods

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Class Variables and Methods

?: Classes are objects.

(X) True ( ) False

?: What type of scope does a class variable have?

( ) Local ( ) Global ( ) Instance (X) Class

?: What is the syntax for a class variable?

( )@variable_name (X)@@variable_name ( )$variable_name ( ) VARIABLE_NAME

?:

def self.class_method_name
  # some code
end

In this code sample, what does the keyword self refer to?

(X) The entire class itself ( ) An instance of the class ( ) Local scope ( ) Instance scope

?: Private methods can only be called within the context of the defining class. The receiver of a private method is always self.

(X) True ( ) False

?: Private methods, including initialize, are usually written with the word "private" above them.

( ) True (X) False

?:

class Book

  attr_accessor :name

  def initialize(name)
    @name = name
  end
end

What syntax should be used to to create a class variables that stores new instances of Book as soon as they're created?

( )

class Book

  @@all = []

  attr_accessor :name

  def initialize(name)
    @name = name
  end
end

( )

class Book
  attr_accessor :name

  def initialize(name)
    @name = name
    @@all << self
  end
end

(X)

class Book

  @@all = []

  attr_accessor :name

  def initialize(name)
    @name = name
    @@all << self
  end
end

( ) None of the Above

?: What type of constant is defined within a class that are available to all instances of a particular class?

( ) Instance ( ) Local ( ) Global (X) Class

?: To create a class constant, what syntax should be used?

( )@variable_name ( )@@variable_name ( )$variable_name (X) VARIABLE_NAME

?:

class Book
  attr_accessor :author, :page_count, :genre
  attr_reader :title

  GENRES = []

  def initialize(title)
    @title = title
  end

  def turn_page
    puts "Flipping the page...wow, you read fast!"
  end

end

If we wanted to modify the above code so that the genre of every Book instance is stored in the GENRES class constant, what needs to change in the above code?

( ) Create the writer for genre and add the logic for the class constant ( ) Add an attr_reader for genre ( ) Remove the attr_accessor for genre (X) All of the Above

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