Ruby module instance and class methods

include.rb

module Foo
  def self.included(base)
    base.extend ClassMethods
  end

  module ClassMethods
    def bar
    end
  end

  def baz
  end
end

class Test
  include Foo
end

Test.bar     # class method
Test.new.bar # No method error
Test.baz     # No method error
Test.new.baz # Instance method