Delegation using rails delegate method

delegation2.rb

require "rails"
module I
  def f
    puts "#{self.class}: doing f()"
  end
 
  def g
    puts "#{self.class}: doing g()"
  end
end
 
 
class A
  include I
end
 
 
class B
  include I
end
 
 
class C
  attr_accessor :i
  delegate :f, :g, :to => :i
 
  def initialize(klass = A)
    self.i = klass.new
  end
end
 
 
c = C.new
c.f         # output: A: doing f()
c.g         # output: A: doing g()
c = C.new(B)
c.f         # output: B: doing f()
c.g         # output: B: doing g()