观察者模式

观察者模式：

    主题发布更新，订阅者收到通知，同步更新自己的业务，达到解耦的目的！

 案例：报社发布报纸，订阅用户收到通知！

   创建主题类接口（InterSubject.php）

<?php


interface InterSubject
{
    //注册订阅者
    public function registerObserver(InterObserver $observer);
    //移除订阅者
    public function removeObserver(InterObserver $observer);
    //订阅变更通知
    public function notifyObserver(NotifyData $notifyData);
}

创建主题实现类（Newspaper.php）

<?php


class Newspaper implements InterSubject
{
    private $observerList = [];
    //注册订阅
    public function registerObserver( InterObserver $observer)
    {
        array_push($this->observerList,$observer);

    }
    //取消订阅
    public function removeObserver(InterObserver $observer)
    {
        $observerList = $this->observerList;
        foreach ($observerList as $key=> $ob){
            if($ob == $observer){
                unset($observerList[$key]);
            }
        }
        $this->observerList = array_values($observerList);
    }

    public function notifyObserver(NotifyData $notifyData)
    {
        foreach ($this->observerList as $observer){
            $observer->update($notifyData);
        }
    }
}

创建订阅者接口（InterObserver.php）

<?php


interface InterObserver
{
    //观察者更新接口
    public function update(NotifyData $notifyData);
}

创建订阅者实现接口（UserA.php）

<?php


class UserA implements InterObserver
{

    public function update(NotifyData $notifyData)
    {
        echo 'I am A ,receive update!eventCode:'.$notifyData->eventCode."\n\r";
    }
}

创建订阅者实现接口（UserB.php）

<?php


class UserB implements InterObserver
{

    public function update(NotifyData $notifyData)
    {
        echo 'I am B ,receive update!eventCode:'.$notifyData->eventCode."\n\r";
    }
}

定义变更数据对象（NotifyData.php）

<?php


class NotifyData
{
    public $eventCode;
    public $eventName;
    public $eventData;
}

定义启动入口（index.php）

<?php
function __autoload($class){
    if ($class) {
        $file = str_replace('\\', '/', $class);
        $file .= '.php';
        if (file_exists($file)) {
            include $file;
        }
    }
}
//实例化主题
$newspager = new Newspaper();
$notifyData = new NotifyData();
//实例化订阅者
$userA = new UserA();
$userB = new UserB();
//订阅
$newspager->registerObserver($userA);
$newspager->registerObserver($userB);
//触发通知
$notifyData->eventCode='first eventCode';
$newspager->notifyObserver($notifyData);
//取消订阅
$newspager->removeObserver($userA);
$notifyData->eventCode='second eventCode';
//触发通知
$newspager->notifyObserver($notifyData);

启动