discountable.rb

module Discountable
  def to_discount_code
    DiscountCode.find_by_code(self)
  end
end
 
class DiscountCode < ActiveRecord::Base
  def to_discount_code
    self
  end
  
  def to_s
    code_string
  end
end
 
my_code = "s8ej1k"
my_code.extend(Discountable)
my_code.to_discount_code # DiscountCode
my_code.to_discount_code # DiscountCode
my_code.to_s # "s8ej1k"

it's like a cup-and-ball game. Watch very carefully... my_code.to_discount_code.to_discount_code.to_s.to_discount_code.to_s.to_s.to_discount_code Ok now, which object has the database ID? :)