Changeable Concern

changeable.rb

module Changeable
  extend ActiveSupport::Concern

  included do
    attr_accessible :type
  end

  module ClassMethods
    def new(attributes = nil, options = {}, &block)
      type = attributes['type'] if attributes.is_a?(Hash)
      if type.blank? || (type = type.constantize) == self
        super(attributes, options, &block)
      else
        super({}, options, &block).becomes(type).tap do |object|
          object.attributes = attributes
        end
      end
    end
  end
end