标签： ruby-on-rails mongoid
attribute_changed?和attribute_was ActiveRecord方法将在after_（创建|更新|保存）回调source
attribute_changed?
attribute_was
Mongoid是否支持mettod saved_change_to_attribute?和attribute_before_last_save以保持一致性？
saved_change_to_attribute?
attribute_before_last_save