如何在PHP中实现完整的Observer模式(How to implement a full Observer pattern in PHP)

 观察者设计模式是松散耦合对象的解决方案，因此它们可以一起工作。 在PHP中，只需使用两个类即可轻松实现。 
 
 基本上，你有一个能够通知和更新观察者状态变化列表的主题。 
 
 我试图解决的问题是知道如何处理提醒观察者关于他们正在观察的对象的不同状态。 
 
 例如，假设我们有一个文件上传类，我们附加了一个日志类，websockets类和一个图像大小调整类。 每个正在观看的课程都希望了解上传过程中的不同事件。 
 
 这个文件上传类可能有三个地方需要通知监听某些事件发生的类。 
 
 
 
 上传时出错（警报记录类） 
 
 
 上传成功（提醒websockets类） 
 
 
 上传成功并且是图像文件（警报图像调整大小类） 
 
 
 这是一个非常基本的例子，但是你如何处理不同观察者可能需要知道的多个事件？ 仅仅调用notifyObservers（）是不够的，因为每个观察者都需要知道它被通知了什么。 
 
 一个想法是，我可以用电话说明正在观察什么类型的事件： 
 
$this->notifyObservers('upload.error', this);
 
 但是，这意味着我将不得不向观察者自己添加自定义切换，以了解如何处理不同的事件。 
 
function observe($type, $object)
{
    if($type === 'upload.error') $this->dosomething();
    elseif($type === 'something.else') $this->otherthing();
    ...etc...
}
 
 我发现这非常丑陋，因为它开始将观察者与他们正在观察的班级相连。 
 
 然后，如果我只是通知观察者而不传递任何关于发生什么事件的信息 - 他们必须猜测自己发生了什么，这意味着如果（）检查更多。 

An Observer Design Pattern is the solution to loosely coupling objects so they can work together. In PHP you can easily implement this using just two classes.
 
Basically, you have a subject which is able to notify and update a list of observers of its state changes.
 
The problem I'm trying to solve is to know how to handler alerting the observers about different states of the object they are watching.
 
For example, lets say we have a file upload class to which we attach a logging class, websockets class, and a image resize class. Each of these classes that are watching want to know about different events in the upload process.
 
This file upload class might have three places where it needs to notify the classes listening that something has happend.
 
 
 
Error With Upload (alert logging class)
 
 
Upload success (alert websockets class)
 
 
Upload success and is image file (alert image resize class)
 
 
This is a very basic example, but how do you handle multiple events that different observers may need to know about? Calling notifyObservers() alone wouldn't be enough since each observer needs to know what it is being notified about.
 
One thought is that I could state with the call what type of event is being observed:
 
$this->notifyObservers('upload.error', this);
 
However, that would mean I would have to add custom switching to the observers themselves to know how to handle different events.
 
function observe($type, $object)
{
    if($type === 'upload.error') $this->dosomething();
    elseif($type === 'something.else') $this->otherthing();
    ...etc...
}
 
I find that very ugly as it starts to couple the observers back to the class they are observing.
 
Then again, if I just notify Observers without passing any information about what event just happens - they have to guess themselves what is going on which means more if() checks.

原文：https://stackoverflow.com/questions/6374294