PHP设计模式：观察者模式

前言

观察者模式属于行为模式，是定义对象间的一种一对多的依赖关系，以便当一个对象的状态发生改变时，所有依赖于它的对象都得到通知并自动刷新。

代码

<?php

//抽象一个观察者
abstract class Observed
{
    abstract function update();
}

//被观察者抽象类
abstract class Observer
{
    private $observeds = []; //被挂载的观察者们

    //加入一个观察者
    public function attach($observed)
    {
        array_push($this->observeds, $observed);
    }

    //移除一个观察者
    public function remove($observed)
    {
        foreach ($this->observeds as &$value) {
            if ($value === $observed) {
                unset($value);
            }
        }
    }

    //通知所有观察者
    public function notify()
    {
        foreach ($this->observeds as &$observed) {
            $observed->update();
        }
    }
}


//创建一个同学类观察目标
class Menber extends Observed
{
    public $name = '';
    public $target;
    public $func;

    public function __construct($name, $target, $func)
    {
        $this->name = $name;
        $this->target = $target;
        $this->func = $func;
    }

    public function update()
    {
        echo $this->name . '观察到目标【' . $this->target->name . '】说：' . $this->target->language . PHP_EOL;
        echo '于是' . call_user_func($this->func);
    }
}

//创建一个目标类（被观察的）
class Target extends Observer
{
    public $name;

    public $language;

    public function __construct($name)
    {
        $this->name = $name;
    }

    public function say($language)
    {
        $this->language = $language;
        echo $this->name . '说：' . $language . PHP_EOL;
    }
}

$target = new Target('蔡旭困');
$target->attach(new Menber('粉丝', $target, function () {
    return '大喊：坤坤你好棒！' . PHP_EOL;
}));
$target->attach(new Menber('黑粉', $target, function () {
    return '嘲讽：律师含！律师含！！' . PHP_EOL;
}));
$target->attach(new Menber('吃瓜群众', $target, function () {
    return '说：鲲之大,一锅炖不下！' . PHP_EOL;
}));
$target->attach(new Menber('狗仔队', $target, function () {
    return '说：明天的头条就是你了！' . PHP_EOL;
}));
$target->say('全民制作人们大家好，我是练习时长两年半的个人练习生，喜欢唱、跳、rap！');
$target->notify();

运行结果

image.png