delegation.rb

module Delegator
  def self.extended(into)
    (class << into; self; end).send :attr_accessor, :delegates
    into.delegates = []

    into.send :define_method, :method_missing do |method, *args, &block|
      self.class.delegates.map{|delegate| send(delegate) }.each do |receiver|
        next unless receiver.respond_to?(method)
        return receiver.send(method, *args, &block)
      end
      super
    end
  end

  def delegate_to(*names)
    @delegates |= names
  end
end

class Engine
  def speed_up
    puts "Go Go Engine Speed Up!"
  end
end

class Chassis
  def transform
    puts "Go Go Chassis transformation!"
  end
end

class Car
  extend Delegator

  delegate_to :engine, :chassis
  attr_reader :engine, :chassis

  def initialize
    @engine = Engine.new
    @chassis = Chassis.new
  end
end

car = Car.new
car.speed_up
car.transform