Forwarding for Ruby composition.

forwarding.rb

# By Barsoom AB <http://barsoom.se> 2012-02-24 under the MIT license.  

require 'active_support/core_ext'

module Forwarding
  def forward(name, opts)
    klass = opts[:to]
    define_method(name) do
      @forwards ||= {}
      @forwards[name] ||= klass.new(self)
    end
    if delegations = opts[:delegate]
      delegate *delegations, :to => name
    end
  end
end

class Customer
  extend Forwarding

  class Naming < Struct.new(:customer)
    def name
      "Pelle"
    end
    def id_and_name
      "#{customer.id}. Pelle"
    end
  end

  class Timing < Struct.new(:customer)
    def age
      42
    end
    def birthday
      "Today!"
    end
  end

  forward :naming, to: Naming,
    delegate: :name

  forward :times, to: Timing,
    delegate: [:birthday, :age]

  def id
    123
  end

end

p Customer.new.name
p Customer.new.naming.name
p Customer.new.naming.id_and_name

p Customer.new.age
p Customer.new.birthday
p Customer.new.times.birthday