ruby_include_idiom.rb

#!/usr/bin/env ruby

module Teacher
  def self.included(model)
    model.instance_eval do
      extend ClassMethods
      include InstanceMethods
    end
  end

  module ClassMethods
    def a_class_method
      "A class method"
    end
  end

  module InstanceMethods
    def a_instance_method
      "An instance method"
    end
  end
end

class Person
  include Teacher
end

p Person.a_class_method
p Person.new.a_instance_method