确定什么属性改变了Rails的after_save回调？ [英] Determine what attributes were changed in Rails after_save callback?

问题描述

我在模型观察器中设置一个after_save回调，只有当模型的已发布属性从false更改为true时，才会发送通知。由于诸如改变之类的方法仅在保存模型之前有用，因此我目前（并未成功）尝试这样做的方式如下：

  def before_save（blog）
 @og_published = blog.published？ 
 end 
 
 def after_save（blog）
如果@og_published == false和blog.published？ == true 
 Notification.send（...）
 end 
 end 
  

$ b b

有没有人有任何建议，最好的方式来处理这个，最好使用模型观察者回调（以免污染我的控制器代码）？

解决方案

在您的 after_update 过滤器中，可以使用 _changed？ c $ c>存取器（至少在Rails 3，不确定Rails 2）。例如：

  class SomeModel< ActiveRecord :: Base 
 after_update：send_notification_after_change 
 
 def send_notification_after_change 
 Notification.send（...）if（self.published_changed？&& self.published == true） 
 end 
 
 end 
  

>


I'm setting up an after_save callback in my model observer to send a notification only if the model's published attribute was changed from false to true. Since methods such as changed? are only useful before the model is saved, the way I'm currently (and unsuccessfully) trying to do so is as follows:

def before_save(blog)
  @og_published = blog.published?
end

def after_save(blog)
  if @og_published == false and blog.published? == true
    Notification.send(...)
  end
end

Does anyone have any suggestions as to the best way to handle this, preferably using model observer callbacks (so as not to pollute my controller code)?

解决方案

In your after_update filter on the model you can use _changed? accessor (at least in Rails 3, not sure for Rails 2). So for example:

class SomeModel < ActiveRecord::Base
  after_update :send_notification_after_change

  def send_notification_after_change
    Notification.send(...) if (self.published_changed? && self.published == true)
  end

end

It just works.

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