lib/active_record_extensions.rb

   1 require 'active_record'
   2
   3 class ActiveRecord::Base
   4   def self.object_id_attr(symbol, klass)
   5     module_eval %{
   6       def #{symbol}
   7         if @#{symbol}.nil? or (@old_#{symbol}_id != #{symbol}_id)
   8           @old_#{symbol}_id = #{symbol}_id
   9           klass = #{klass}.descendants.find { |d| d.#{symbol}_name == #{symbol}_id }
  10           klass ||= #{klass}
  11           @#{symbol} = klass.new
  12         else
  13           @#{symbol}
  14         end
  15       end
  16     }
  17   end
  18 end