PHP design pattern observer pattern, php design pattern observer_PHP tutorial

PHP design pattern observer pattern, PHP design pattern observer

Introduction There are two schools now. Some people recommend using design patterns, and some people don’t recommend using design patterns!
This is just like writing an article. Some people like articles to follow a routine, such as narrative articles, time, place, characters, and events. And some people like to write essays or prose, and some people like to write poetry!

Nowadays, writing code is similar to writing articles in many ways, but in some places it requires more skills than writing articles! If you write too much, you can usually write excellent articles, and the same goes for code. If you write too much, you can also write a lot of good code!

Many times, when I look at design patterns, some design patterns just fit my coding habits. But if you forcefully try to do it, it will be counterproductive. ——Most of the time, you have to learn the moves and use them unconsciously in the application to master them. But don’t stick to the moves. Is it true that “there is a move to win without a move”? ​ My original intention of learning design patterns was to know that there was such a thing? If you have this impression in your mind, you won’t be confused by it! If the design pattern does not conform to your habits, it will be detrimental to your code reading! ​ The Observer pattern defines one-to-many dependencies of objects, so that when an object changes state, all of its dependencies will be notified and updated automatically! ​ design principles ​ In the observer pattern, what changes is the status of the subject and the number of observers. Using this pattern, you can change objects that depend on the theme's state without changing the theme. --Find the aspects of your program that change and separate them from the aspects that are fixed! ​ Both subjects and observers use interfaces: observers use the subject's interface to register with the subject, and the subject uses the observer interface to notify observers. This allows the two to operate normally while also having the advantage of loose coupling! ——For interface programming, not implementation programming! . The observer pattern uses "composition" to combine many observers into topics. This relationship between objects (observers - subjects) is not generated through inheritance, but through composition at runtime.——Use more combination and less inheritance! ​ code ​

<?php /** * 观察者模式 * @author: Mac */ class Paper{ /* 主题 */ private $_observers = array(); public function register($sub){ /* 注册观察者 */ $this->_observers[] = $sub;     }             public function trigger(){  /*  外部统一访问    */         if(!empty($this->_observers)){             foreach($this->_observers as $observer){                 $observer->update();             }         }     } }   /**  * 观察者要实现的接口  */ interface Observerable{     public function update(); }   class Subscriber implements Observerable{     public function update(){         echo "Callbackn";     } }

The following is the test code

/*  测试    */ $paper = new Paper(); $paper->register(new Subscriber()); //$paper->register(new Subscriber1()); //$paper->register(new Subscriber2()); $paper->trigger();

Summarize ​​​​ When a new object is to be filled in, you only need to register it in the subject (also called an observable) (there are many registration methods, you can also register during construction, or in the interface accessed by the framework), and then implement the code directly Do it in the interface of the new object. This reduces the coupling between subject and observer objects. ​ Good design patterns don't go directly into your code, they go into your brain.

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