Review PHP设计模式之——观测模式

观测模式：

 <?php
 class car implements SplSubject{
     private $carName;    //车的类型
     private $carState=0; //车的状态，0为关闭，1这启动车子
     private $carSpeed=0; //初始化车的速度表值
     private $Observers;  //各项车的性能观察对象

     public function __construct($Name){
         $this->carName=$Name;
         $this->Observers=new SplObjectStorage;
     }

     //启动
     public function start(){
         $this->carState=1;
         $this->notify();
     }

     //停车
     public function stop(){
         $this->carState=0;
         $this->carSpeed=0;
         $this->notify();
     }

     //加速
     public function accelerate($Acceleration){
         if(0===$this->carState){
             throw new Exception('Please start!');
         }
         if(!is_int($Acceleration) || $Acceleration<0){
             throw new Exception('The value of acceleration is invalid!');
         }
         $this->carSpeed+=$Acceleration;
         $this->notify();
     }

     //增加监测对象
     public function attach(SplObserver $observer){
         if(!$this->Observers->contains($observer)){
             $this->Observers->attach($observer);
         }
         return true;
     }

     //删除监测对象
     public function detach(SplObserver $observer){
         if(!$this->Observers->contains($observer)){
             return false;
         }
         $this->Observers->detach($observer);
         return true;
     }

     //传送对象
     public function notify(){
         foreach($this->Observers as $observer){
             $observer->update($this);
         }
     }

     public function __get($Prop){
         switch($Prop){
             case 'STATE':
                 return $this->carState;
                 break;
             case 'SPEED':
                 return $this->carSpeed;
                 break;
             case 'NAME':
                 return $this->carName;
                 break;
             default:
                 throw new Exception($Prop.'can not be read');
         }
     }

     public function __set($Prop,$Val){
         throw new Exception($Prop.'can not be set');
     }
 }

 class carStateObserver implements SplObserver{
     private $SubjectState;
     public function update(SplSubject $subject){
         switch($subject->STATE){
             case 0:
                 if(is_null($this->SubjectState)){
                     echo $subject->NAME.' not started'."\n";
                 }else{
                     echo $subject->NAME.' stalling of engine'."\n";
                 }
                 $this->SubjectState=0;
                 break;
             case 1:
                 if(1!==$this->SubjectState){
                     echo $subject->NAME.' is starting'."\n";
                     $this->SubjectState=1;
                 }
                 break;
             default:
                 throw new Exception('Unexpected error in carStateObserver::update()');
         }
     }
 }

 class carSpeedObserver implements SplObserver{
     public function update(SplSubject $subject){
         if(0!==$subject->STATE){
             echo $subject->NAME.' current speed is '.$subject->SPEED.'Kmh'."\n";
         }
     }
 }

 class carOverspeedObserver implements SplObserver{
     public function update(SplSubject $subject){
         if($subject->SPEED>130){
             throw new Exception('The max speed is 130, you are breaking up!'."\n");
         }
     }
 }

 try{
     $driver = new car('AUDIA4');
     $driver->attach(new carStateObserver);
     $driver->attach(new carSpeedObserver);
     $driver->attach(new carOverspeedObserver);
     $driver->start();
     $driver->accelerate(10);
     $driver->accelerate(30);
     $driver->stop();
     $driver->start();
     $driver->accelerate(50);
     $driver->accelerate(70);
     $driver->accelerate(100);
     $driver->accelerate(150);
 }
 catch(Exception$e){
     echo $e->getMessage();
 }
 ?>