# encoding: utf-8
 
# Two ways of extending a class by class methods.
module M
  module ClassMethods
    def one
      'ok!'
    end
 
    def two
      'ok two!'
    end
  end
end
 
# I
class TestOne
  class << self
    include M::ClassMethods
  end
end
 
# II
class TestTwo
  extend M::ClassMethods
end
 
puts [
  TestOne.one, #=> ok!
  TestOne.two  #=> ok two!
]
 
puts [
  TestTwo.one, #=> ok!
  TestTwo.two  #=> ok two!
]