PHP观察者模式有什么用，实现代码是什么-群英

上一篇：PHP职责链模式怎样实现，代码是什么下一篇：PHP中Imagick实现图像直方图怎样做的

这篇文章主要讲解了“PHP观察者模式有什么用，实现代码是什么”，文中的讲解内容简单、清晰、详细，对大家学习或是工作可能会有一定的帮助，希望大家阅读完这篇文章能有所收获。下面就请大家跟着小编的思路一起来学习一下吧。

代码如下:

 
  /**
 
 * 观察者模式
 
 *
 
 * 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
 
 * 能够便利地创建查看目标对象状态的对象,并且提供与核心对象非耦合的指定功能
 
 * 插件系统
 
 */
 
 class Observerable
 
 {
 
 private $_observers = array();
 
 public function registerObserver($observer)
 
 {
 
 $this->_observers[] = $observer;
 
 }
 
 public function removeObserver($observer)
 
 {
 
 $key = array_search($observer,$this->_observers);
 
 if(!($key === false))
 
 {
 
 unset($this->_observers[$key]);
 
 }
 
 }
 
 public function notifyObservers()
 
 {
 
 foreach($this->_observers as $observer)
 
 {
 
 if($observer instanceof Observer) $observer->update($this);
 
 }
 
 }
 
 }
 
 interface Observer
 
 {
 
 public function update($observer);
 
 }
 
 interface DisplayElement
 
 {
 
 public function display();
 
 }
 
 // -- 实例类定义
 
 class NewsObserverable extends Observerable
 
 {
 
 private $_sports_news;
 
 public function setSportsNews($data)
 
 {
 
 $this->_sports_news = $data;
 
 $this->notifyObservers();
 
 }
 
 public function getSportsNews()
 
 {
 
 return $this->_sports_news;
 
 }
 
 private $_local_news;
 
 public function setLocalNews($data)
 
 {
 
 $this->_local_news = $data;
 
 $this->notifyObservers();
 
 }
 
 public function getLocalNews()
 
 {
 
 return $this->_local_news;
 
 }
 
 }
 
 class SportsNews implements Observer,DisplayElement
 
 {
 
 private $_data = null;
 
 public function update($observer)
 
 {
 
 if($this->_data != $observer->getSportsNews())
 
 {
 
 $this->_data = $observer->getSportsNews();
 
 $this->display();
 
 }
 
 }
 
 public function display()
 
 {
 
 echo $this->_data.date("Y-m-d H:i:s")."
 
";
 
 }
 
 }
 
 class LocalNews implements Observer,DisplayElement
 
 {
 
 private $_data = null;
 
 public function update($observer)
 
 {
 
 if($this->_data != $observer->getLocalNews())
 
 {
 
 $this->_data = $observer->getLocalNews();
 
 $this->display();
 
 }
 
 }
 
 public function display()
 
 {
 
 echo $this->_data.date("Y-m-d H:i:s")."
 
";
 
 }
 
 }
 
 // -- 实例化 ---
 
 $objObserver = new NewsObserverable();
 
 $local = new LocalNews();
 
 $sports = new SportsNews();
 
 $objObserver->registerObserver($local);
 
 $objObserver->registerObserver($sports);
 
 $objObserver->setSportsNews("sports news 1 ");
 
 $objObserver->setLocalNews("local news 1 ");
 
 $objObserver->removeObserver($sports);
 
 $objObserver->setLocalNews("local news 2 ");
 
 $objObserver->setSportsNews("sports news 2 ");
 
 $objObserver->removeObserver($local);
 
 $objObserver->setLocalNews("local news 3 ");