Delegation pitfals vs extend

gistfile1.rb

require 'delegate'

class Person
  def greeting
    'hello'
  end

  def speak
    greeting
  end
end

class LatinDecorator < SimpleDelegator
  def greeting
    "hola"
  end

  def listen
    "OK"
  end
end

class GermanDecorator
  def self.new(object)
    object.instance_eval do
      def greeting
        "Hallo"
      end
    end
    object
  end
end


person  = Person.new
puts LatinDecorator.new(person).speak
puts LatinDecorator.new(person).greeting
puts GermanDecorator.new(person).speak
puts GermanDecorator.new(person).greeting