观察者vs.回调 [英] Observers vs. Callbacks

问题描述

我想过使用观察者或回调。
什么时候应该使用观察者？

i thought about using observers or callbacks. What and when you should use an observer?

您可以执行以下操作：

# User-model
class User << AR
  after_create :send_greeting!

  def send_greeting!
    UserNotifier.deliver_greeting_message(self)
  end

end

#observer
class UserNotifier << AR
  def greeting_message(user)
  ...
  end
end

b $ b

或者你可以创建一个观察者并让它在用户创建时观看...

or you could create an observer and let it watch when users becomes created...

你推荐了什么？

推荐答案

回调函数的生命周期更短：将它传递给一个被调用的函数。它是API的一部分，因为你通常不能调用该函数而不传递回调。这个概念与该功能紧密耦合。通常，您只能传递一个回调..

A callback is more short lived: You pass it into a function to be called once. It's part of the API in that you usually can't call the function without also passing a callback. This concept is tightly coupled with what the function does. Usually, you can only pass a single callback..

示例：运行一个线程并给出一个回调，当线程终止时调用。

Example: Running a thread and giving a callback that is called when the thread terminates.

观察者寿命更长，可以随时连接/分离。

An observer lives longer and it can be attached/detached at any time. There can be many observers for the same thing and they can have different lifetimes.

示例：在UI中显示模型中的值，并从用户输入更新模型。

Example: Showing values from a model in a UI and updating the model from user input.

这篇关于观察者vs.回调的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！