class instance variables

gistfile1.rb

class Foo
  class << self #anything inside this is executed in the context of the class object
    attr_accessor :bar

    def upcase_bar
      @bar.upcase
    end
  end

  def self.downcase_bar #also, in the class definition, self also refers to the class object
    @bar.downcase
  end
end

Foo.bar = "lol"

Foo.bar
  => "lol"

Foo.upcase_bar
  => "LOL"

Foo.downcase_bar
  => "lol"