在委托模式中,复制代码 代码如下

 应用     |      2020-03-11 21:46

复制代码 代码如下:

复制代码 代码如下:

        委托模式是软件设计模式中的一项基本技巧。在委托模式中,有两个对象参与处理同一个请求,接受请求的对象将请求委托给另一个对象来处理。委托模式是一项基本技巧,许多其他的模式,如状态模式、策略模式、访问者模式本质上是在更特殊的场合采用了委托模式。

/**
* 委托模式 示例
*
* @create_date: 2010-01-04
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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();
?>

_object = new $object(); } function addSong { $this->_songs[] = array("location"=>$location,"title"=>$title); } function getPlayList() { return $this->_object->getPlayList; } } class mp3PlayListDelegation { function getPlayList { $aResult = array(); foreach($songs as $key=>$item) { $path = pathinfo; if(strtolower == "mp3") { $aResult[] = $item; } } return $aResult; } } class rmvbPlayListDelegation { function getPlayList { $aResult = array(); foreach($songs as $key=>$item) { $path = pathinfo; if(strtolower == "rmvb") { $aResult[] = $item; } } return $aResult; } } $oMP3PlayList = new PlayList; $oMP3PlayList->getPlayList(); $oRMVBPlayList = new PlayList; $oRMVBPlayList->getPlayList(); ?>

        动态委托的介绍:动态委托概念来自于Jakarta 字节码工程库 (Byte-Code Engineering Library, BCEL)。它能够分析存在的类,并且对于接口,抽象类,甚至运行时的具体类来说,它能够生成以字节编码委托类。

        被委托的接口/类应该满足如下条件:动态委托最多只能委托一个类,但是能够代理多个接口。这个限制来自于Java的单继承模式。一个Java类最多只有一个父类。既然生成的委托类把被委托类作为它的父类,那么指定多个被委托类是不合理的。如果没有指定被委托类,那么缺省的父类就是Object。

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下面是PHP 反射机制实现动态代理的代码:

class Fruit 

{   

        function callFruit()   

        {    

                echo "Generate an Apple";  

        } 

class FruitDelegator

        private $targets;  

        function __construct()  

        {    

                $this->target[] = new Fruit();  

        }     

        function __call($name, $args)   

        {    

                foreach ($this->target as $obj)    {      

                        $r = new ReflectionClass($obj);      

                        if ($method = $r->getMethod($name))       {         

                                if ($method->isPublic() && !$method->isAbstract())        {           

                                        return $method->invoke($obj, $args);        

                                }       

                        }     

                }  

        } 

$obj = new FruitDelegator(); 

$obj->callFruit(); 

// 运行结果 

// Generate an Apple

        可见,通过代理类FruitDelegator来代替Fruit类来实现他的方法。同样的,如下的代码也是能够运行的:

class Color

{  

        function callColor()  

        {    

                echo "Generate Red";  

        }

}

class ColorDelegator

{  

        private $targets;  

        function addObject($obj)  

        {    

                $this->target[] = $obj;  

        }  

        function __call($name, $args)  

        {    

                foreach ($this->target as $obj)    {      

                        $r = new ReflectionClass($obj);      

                        if ($method = $r->getMethod($name))      {        

                                if ($method->isPublic() && !$method->isAbstract())        {          

                                        return $method->invoke($obj, $args);        

                                }      

                        }    

                }  

        }

}

$obj = new ColorDelegator();

$obj->addObject(new Color());

$obj->callColor();

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        设计了一个CD类,类中有mp3播放模式,和mp4播放模式;改进前,使用cd类的播放模式,需要在实例化的类中去判断选择什么方式的播放模式 ;改进后,播放模式当做一个参数传入playList函数中,就自动能找到对应需要播放的方法。

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未改进前

//使用委托模式之前,调用CD类,选择CD播放模式是复杂的选择过程

class cd

        protected $cdInfo = array(); 

        public function addSong($song)

        {  

                $this->cdInfo[$song] = $song; 

        } 

        public function playMp3($song)

        {  

                return $this->cdInfo[$song] . '.mp3'; 

        } 

        public function playMp4($song)

        {  

                return $this->cdInfo[$song] . '.mp4'; 

        }

}

$oldCd = new cd;

$oldCd->addSong("1");

$oldCd->addSong("2");

$oldCd->addSong("3");

$type = 'mp3';

if ($type == 'mp3') { 

        $oldCd->playMp3();

} else { 

        $oldCd->playMp4();

}

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        通过委托模式,改进后的CD类

namespace Tools;

/*

**委托模式

**去除核心对象中的判决和复杂功能性

*/

//委托接口

interface Delegate

        public function playList($list,$song);

}

//mp3处理类

class mp3 implements Delegate

        public function playList($list,$song)

        {  

                return $list[$song].'.mp3'; 

        }

}

//mp4处理类

class mp4 implements Delegate

        public function playList($list, $song) 

        {  

                return $list[$song].'.mp4'; 

        }

}

class cdDelegate

        protected $cdInfo = array(); 

        public function addSong($song)

        {  

                $this->cdInfo[$song] = $song; 

        } 

        public function play($type,$song)

        {  

                $name = 'Tools\'.$type;  

                $obj = new $name;  

                return $obj->playList($this->cdInfo,$song); 

        }

}

$newCd = new cdDelegate();

$newCd->addSong("1");

$newCd->addSong("2");

$newCd->addSong("3");

echo $newCd->play('mp3','1');

//只要传递参数就能知道需要选择何种播放模式

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再为大家分享一个实例:

/** 

**委托模式 示例 

*/

class PlayList

        var $_songs = array(); 

        var $_object = null; 

        public function PlayList($type) 

        {  

                $object = $type."PlayListDelegation";  

                $this->_object = new $object(); 

        } 

        public function addSong($location,$title) 

        {  

                $this->_songs[] = array("location"=>$location,"title"=>$title); 

        } 

        public function getPlayList() 

        {  

                return $this->_object->getPlayList($this->_songs); 

        }

}

class mp3PlayListDelegation

        public 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

        public 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();

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