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What is the observer pattern in PHP? How to use it?

慕斯
慕斯Original
2021-06-23 11:23:021620browse

We may not be so familiar with the observer pattern. It is an event system, which means that this pattern allows a class to observe the state of another class. When the state of the observed class changes, When, the observation class can receive notifications and take corresponding actions; the observer pattern provides another way to avoid tight coupling between components; so let’s discuss what the observer pattern is in this article!

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Observer:

It is an event system, which means that this pattern allows a class to observe the state of another class when When the state of the observed class changes, the observing class can receive notifications and take corresponding actions; the observer pattern provides another way to avoid tight coupling between components;

We still use code For example, we create a new file, then define a class, and then write a member attribute in the class, which is an array to store observers, and then we define a method, which is used to store observers and Adding an observer allows the observer to be notified and make a certain response when the observed behavior is performed. The code is as an example:

<?php
class Man
{
//用来存放观察者
protected $observers = [];
//添加观察者方法
function addObserver($observer)
{
  $this->observers[]=$observer;
}
//花钱方法
function buy()
{
//当被观察者做出这个行为的时候,让观察者得到通并且做出一-定的反应
foreach ($this->observers as $girl) {
  $girl->pome();
}
}
}
class GirlFriend
{
function pome()
{
echo&#39;我只明白一件事,爱一个人,是那么痛苦<br />&#39;;
}
}
//创建对象
$xiaoming = new Man();
$xiaohua =new GirlFriend();
$xiaoli = new GirlFriend();
//添加观察者
$xiaoming->addObserver( $xiaohua); 
$xiaoming->addObserver($xiaoli);
$xiaoming->buy();

The running results are as follows:

What is the observer pattern in PHP? How to use it?

If there is a method to add an observer, then there is a method to delete an observer, so we also need to add a method to delete an observer,

function delObserver($observer)
{
//查找对应值在数组中的键
$key = array_search($observer,$this->observers);
//根据键删除值,并且数组重新索引
array_splice($this->observers, $key, 1);
}
}

//Delete

$xiaoming->delObserver( $xiaohua);

The code is as follows:

What is the observer pattern in PHP? How to use it?

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