PHP设计模式系列 - 委托模式

    <?php  
    //委托模式-去除核心对象中的判决和复杂的功能性  
    //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();  
    }  

    <?php  
    //委托模式-去除核心对象中的判决和复杂的功能性  
    //改进cd类  
    class cdDelegate {  
        protected $cdInfo = array();   
          
        public function addSong($song) {  
            $this->cdInfo[$song] = $song;  
        }  
          
        public function play($type, $song) {  
            $obj = new $type;  
            return $obj->playList($this->cdInfo, $song);  
        }  
    }  
      
    class mp3 {  
        public function playList($list) {  
            return $list[$song];  
        }  
    }  
      
    class mp4 {  
        public function playList($list) {  
            return $list[$song];  
        }  
    }  
      
    $newCd = new cd;  
    $newCd->addSong("1");  
    $newCd->addSong("2");  
    $newCd->addSong("3");  
    $type = ‘mp3‘;  
    $oldCd->play(‘mp3‘, ‘1‘); //只要传递参数就能知道需要选择何种播放模式