设计模式-观察者模式

<?php
/* 
 *观察者模式：观察者设计模式能够更便利的创建和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性
 */


class CD{


    public $title = '';
    public $band = "";
    protected $_observers = array();


    public function  __construct( $title, $band) {
        $this->title = $title;
        $this->band = $band;
    }


    public function attachObserver( $type, $observer){
        $this->_observers[$type][] = $observer;
    }


    public function notifyObserver($type){
        if(isset ($this->_observers[$type])){


            foreach($this->_observers[$type] as $observer){
                $observer->update($this);
            }
        }
    }


    public function buy(){
        $this->notifyObserver("purchased");
    }
    






}


class buyCDNotifyStreamObserver{


    public function update(CD $cd){


        $activity = "The CD namde {$cd->title} by";
        $activity.="{$cd->band} was just purchased";
        activityStream::addNewItem( $activity);
    }


}


class activityStream{
    
    public static function addNewItem($item){
        print $item;
    }
}


$title = 'waste of a rib';
$band = 'never again';
$cd = new CD($tiltle, $band);
$observer = new buyCDNotifyStreamObserver();
$cd->attachObserver($type, $observer);
$cd->buy();
















?>