Taken from http://coderrr.wordpress.com/2008/04/22/building-the-right-class-with-sti-in-rails/

STI_Example.rb

#Taken from http://coderrr.wordpress.com/2008/04/22/building-the-right-class-with-sti-in-rails/


class GenericClass < ActiveRecord::Base
  class << self
    def new_with_cast(*a, &b)
      if (h = a.first).is_a? Hash and (type = h[:type] || h['type']) and (klass = type.constantize) != self
        raise "wtF hax!!"  unless klass < self  # klass should be a descendant of us
        return klass.new(*a, &b)
      end

      new_without_cast(*a, &b)
    end
    alias_method_chain :new, :cast
  end
end

class X < GenericClass; end
GenericClass.new(:type => 'X') # => #<X:0xb79e89d4 @attrs={:type=>"X"}>