cattr_accessor vs class_attibute

gistfile1.rb

# cattr_accessor

class Base
  cattr_accessor :settings

  # def self.settings
  #   @@settings
  # end

  # def self.settings=(value)
  #   @@settings = value
  # end
end

#Class variable have a tendency to wander from class to class. @@settings class variable can be exposed through inheritance tree.

class Subclass < Base
end

>> Base.settings = 'foo'
>> Subclass.settings # => 'foo'
>> Subclass.settings = 'bar'
>> Base.settings # => 'bar'

# class_attribute

class Base
  class_attribute :settings

  # def self.settings
  #   nil
  # end

  # def self.settings?
  #   !!settings
  # end

  # def self.settings=(value)
  #   # store value in singleton class
  #   # by redefining `settings` method each time
  # end
end

#Settings value is inheritable by subclasses. Subclasses can change their own value and it will not impact base class.

class Subclass < Base
end

>> Base.settings = 'foo'
>> Subclass.settings # => 'foo'
>> Subclass.settings = 'bar'
>> Base.settings # => 'foo'


# Above code snippets are extracted from some online content