php设计模式之委托模式

php设计模式之委托模式

<?php
/**
* 原来的程序写法
* @var playlist
*/
$playlist = new playlist();
$playlist->addSong('/home/aaron/music/aa.mp3', 'Brr');
$playlist->addSong('/home/aaron/music/bb.mp3', 'GoodBye');
if ($extType == 'pls') {
$playlistContent = $playlist->getPLS();
} else {
$playlistContent = $playlist->getM3U();
}

上述仅仅是一个示例，如果有更多的Type，那么这里的if/else将会有多个并且每次增加类型需要增加方法。而接下来的委托模式将改变这个现状。委托模式的类在需求改变时候需要修改。

/**
* 委托模式的类
*/
class newPlaylist
{
private $__songs;
private $__typeObject;
public function __construct($type)
{
$this->__songs = array();
$object = "{$type}Playlist";
$this->__typeObject = new $object;
}

public function addSong($location, $title)
{
$song = array('location' => $location, 'title'=>$title);
$this->__songs[] = $song;
}

public function getPlaylist()
{
$playlist = $this->__typeObject->getPlaylist($this->__songs);
return $playlist;
}
}

/**
* m3u   Delegate
*/
class m3uPlaylistDelegate
{

public function getPlaylist($songs)
{
$m3u = "#EXTM3U\n\n";
}

/*
other function
*/
}
/**
* pls    Delegate
*/
class plsPlaylistDelegare
{

function getPlaylist($songs)
{
$pls=" ";
}
}

每增加一种类型只需要增加一个对应的类即可，并且注意写法要统一，具体使用方法中将不存在if/else的判断。示例如下。

/**
* 如何使用
*/
$extType = 'pls';//$extTyle = 'm3u';
$playlist = new newPlaylist($extType);
$playlistContent = $playlist->getPlaylist();