php设计模式 Observer(观察者模式)

<div class="codetitle"><a style="CURSOR: pointer" data="24554" class="copybut" id="copybut24554" onclick="doCopy('code24554')"> 代码如下:<div class="codebody" id="code24554">
<?php
/*
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 ");

（编辑：李大同）

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