行为型设计模式: 观察者模式 observer
当对象的状态发生变化时，所有依赖于它的对象都得到通知并被自动更新。它使用的是低耦合的方式。
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| <?php
interface Observer
{
public function update(Subject $subject): void;
}
class ConcreteObserver implements Observer
{
private $observerState = '';
function update(Subject $subject): void
{
$this->observerState = $subject->getState();
echo '执行观察者操作！当前状态：' . $this->observerState;
}
}
class Subject
{
private $observers = [];
private $stateNow = '';
public function attach(Observer $observer): void
{
array_push($this->observers, $observer);
}
public function detach(Observer $observer): void
{
$position = 0;
foreach ($this->observers as $ob) {
if ($ob == $observer) {
array_splice($this->observers, ($position), 1);
}
++$position;
}
}
public function notify(): void
{
foreach ($this->observers as $ob) {
$ob->update($this);
}
}
}
class ConcreteSubject extends Subject{
public function setState($state)
{
$this->stateNow = $state;
$this->notify();
}
public function getState()
{
return $this->stateNow;
}
}
|
可以在 Subject 里仅注重其本身的业务逻辑, 对于观察者模式下对观察者的notify 操作改为 implement 一个接口来实现, 使其 observable ?
SPL扩展实现观察者模式-完整源码：
https://github.com/zhangyue0503/designpatterns-php/blob/master/06.observer/source/spl_observer.php