设计模式之观察者模式(php实现)

Posted 2020-11-17 周起

github地址:https://github.com/ZQCard/design_pattern

/**
 * 当对象间存在一对多关系时，则使用观察者模式（Observer Pattern）。
 * 比如，当一个对象被修改时，则会自动通知它的依赖对象。观察者模式属于行为型模式。
 * 一个对象（目标对象）的状态发生改变，所有的依赖对象（观察者对象）都将得到通知，进行广播通知。
 */

(1) Subject.class.php（目标类）

<?php

namespace Observer;

class Subject
{
    private $state;

    private $observers = [];

    public function getState()
    {
        return $this->state;
    }

    public function seState($state)
    {
        $this->state = $state;
        $this->notifyAllObjects();
    }

    public function register(Observer $object)
    {
        $this->observers[] = $object;
    }

    public function remove($object)
    {
        foreach ($this->observers as $key => $observer) {
            if ($observer == $object){
                unset($this->observers[$key]);
            }
        }
    }

    public function notifyAllObjects()
    {
        foreach ($this->observers as $observer) {
            $observer->update();
        }
    }
}

(2)Observer.class.php（观察者抽象父类）

<?php

namespace Observer;

abstract class Observer
{
    protected $subject;

    public abstract function update();
}

(3)ObjectA.class.php （具体抽象类A）

<?php

namespace Observer;

class ObserverA extends Observer
{
    private $myState = ‘init A‘;

    public function __construct(Subject $subject)
    {
        $this->subject = $subject;
        $this->subject->register($this);
    }

    public function update()
    {
        $this->myState = $this->subject->getState();
    }

    public function getSate()
    {
        return "ObserverA get state:".$this->myState;
    }
}

(4)ObserverB.class.php（具体观察者B）

<?php

namespace Observer;

class ObserverB extends Observer
{
    private $myState = ‘init B‘;

    public function __construct(Subject $subject)
    {
        $this->subject = $subject;
        $this->subject->register($this);
    }

    public function update()
    {
        $this->myState = $this->subject->getState();
    }

    public function getSate()
    {
        return "ObserverB get state:".$this->myState;
    }
}

（5）observer.php

<?php

spl_autoload_register(function ($className){
    $className = str_replace(‘\‘,‘/‘,$className);
    include $className.".class.php";
});

use ObserverObserverA;
use ObserverObserverB;
use ObserverSubject;
/*

ObserverA get state:init A
ObserverB get state:init B
ObserverA get state:hello
ObserverB get state:hello
*/

$subject = new Subject(); $objectA = new ObserverA($subject); $objectB = new ObserverB($subject); echo $objectA->getSate(); echo ‘<br/>‘; echo $objectB->getSate(); echo ‘<br/>‘; $subject->seState("hello"); echo $objectA->getSate(); echo ‘<br/>‘; echo $objectB->getSate(); echo ‘<br/>‘;