php设计模式 Delegation (委托模式)

<?php
/**
 * 委托模式 示例
 *
 * @create_date: 2010-01-04
 */
class PlayList
{
    var $_songs = array();
    var $_object = null;
 
    function PlayList($type)
    {
        $object = $type."PlayListDelegation";
        $this->_object = new $object();
    }
 
    function addSong($location,$title)
    {
        $this->_songs[] = array("location"=>$location,"title"=>$title);
    }
 
    function getPlayList()
    {
        return $this->_object->getPlayList($this->_songs);
    }
}
 
class mp3PlayListDelegation
{
    function getPlayList($songs)
    {
        $aResult = array();
        foreach($songs as $key=>$item)
        {
            $path = pathinfo($item['location']);
            if(strtolower($item['extension']) == "mp3")
            {
                $aResult[] = $item;
            }
        }
        return $aResult;
    }
}
 
class rmvbPlayListDelegation
{
    function getPlayList($songs)
    {
        $aResult = array();
        foreach($songs as $key=>$item)
        {
            $path = pathinfo($item['location']);
            if(strtolower($item['extension']) == "rmvb")
            {
                $aResult[] = $item;
            }
        }
        return $aResult;
    }
}
 
$oMP3PlayList = new PlayList("mp3");
$oMP3PlayList->getPlayList();
$oRMVBPlayList = new PlayList("rmvb");
$oRMVBPlayList->getPlayList();