mind_blown.rb

module Lib
  def xpto(option)
    mod = Module.new
    include mod
    mod.class_eval <<-RUBY, __FILE__, __LINE__+1
      def #{option}
        1
      end
    RUBY
  end
end

class Model
  extend Lib
  xpto 'a'
end

m = Model.new
p m.a # 1

module Foo

  def respond_to(name)
    define_method(name) { "i have #{name} on #{self.class}" }
  end

end

class ModelFoo
  extend Foo

  def foo
    "oops"
  end

  respond_to 'foo'
end

class ModelBar
  extend Foo
  respond_to 'bar'
end


foo = ModelFoo.new
foo.foo

module Foo

  def respond_to(name)
    define_method(name) { "i have #{name} on #{self.class}" }
  end

end

class ModelFoo
  extend Foo
  respond_to 'foo'

  def foo
    "oops"
  end

end


foo = ModelFoo.new
foo.foo
# => 'oops'