<?php
/**
* 觀察者模式
*
* 定義對象間的一種一對多的依賴關(guān)系,以便當(dāng)一個對象的狀態(tài)發(fā)生改變時,所有依賴于它的對象都得到通知并自動刷新
* 能夠便利地創(chuàng)建查看目標(biāo)對象狀態(tài)的對象,并且提供與核心對象非耦合的指定功能
* 插件系統(tǒng)
*/
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();
}

// -- 實例類定義
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")."<br/>";
}
}

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")."<br/>";
}
}

// -- 實例化 ---

$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 ");