《Head First设计模式》读书笔记（二）

对于观察者模式,PHP通过标准PHP库(SPL)提供了内建的支持，下面用SPL对昨天的观察者模式示例进行修改。

代码

<? php
     class  WeatherData  implements  SplSubject
    {
         private   $observers   =   null ;
         private   $temperature   =   0 ;
         private   $humidity   =   0 ;
         private   $pressure   =   0 ;
         public  __construct()
        {
             $this -> observers  =   new  SplObjectStorage();
        }
         public   function  getTemperature()
        {
             return   $this -> temperature;
        }
         public   function  setTemperature( $temp )
        {
             $this -> temperature  =   $temp ;
        }    
         public   function  getHumidity()
        {
             return   $this -> humidity;
        }
         public   function  setHumidity( $humidity )
        {
             $this -> humidity  =   $humidity ;
        }
         public   function  getPressure()    
        {
             return   $this -> pressure;
        }
         public   function  setPressure( $pressure )
        {    
             $this -> pressure  =   $pressure ;
        }
         public   function  setMeasurements( $temperature ,   $humidity ,   $pressure ) 
        {
             $this -> setTemperature( $temperature );
             $this -> setHumidity( $humidity );
             $this -> setPressure( $pressure );
             $this -> measureChanged();            
        }
         public   function  measureChanged()
        {
             $this -> notify();
        }
         public   function  attach(SplObserver  $observer )
        {
             $this -> observers -> attach( $observer );
        }
         public   function  detach(SplObserver  $observer )
        {
             $this -> observers -> detach( $observer );
        }
         public   function  notify()
        {
             foreach  ( $this -> observers  as   $observer ) {
                 $observer -> update( $this );
            }
        }
         public   function  getObservers() 
        {
             return   $this -> observers;
        }
    }
     abstract   class  BaseDisplay  implements  SplObserver
    {
         private   $weatherData   =   null ; 
         public   function  __construct(WeatherData  $weatherData   =   null )
        {
             $this -> weatherData  =   $weatherData ;
             if  ( $weatherData   !=   null ) {
                 $this -> weatherData -> attach( $this );
            }
        }
         public   function  update(SplSubject  $subject )
        {
             if  ( $subject   ===   $this -> weatherData) {
                 $this -> realUpdate( $subject );
            }
        }
         abstract   function  realUpdate(WeatherData  $weatherData );
    }
     class  CurrentConditionDisplay  extends  BaseDisplay
    {
         private   $temperature   =   0 ;
         private   $humidity   =   0 ;
         private   $pressure   =   0 ;
         function  realUpdate(WeatherData  $weatherData )    
        {
             $this -> temperature  =   $weatherData -> getTemperature();
             $this -> humidity  =   $weatherData -> getHumidity();
             $this -> pressure  =   $weatherData -> getPressure();
             print ( " temp:  "   .   $this -> temperature  .   " , humi:  "   .   $this -> humidity  .   " , pressure:  "   .   $this -> pressure  .   " /n " );
        }
    }
     class  GeneralDisplay  extends  BaseDisplay
    {
         function  realUpdate(WeatherData  $weatherData )    
        {
             print ( " GeneralDisplay/n " );
        }
    }
     $weatherData   =   new  WeatherData();
     $display   =   new  CurrentConditionDisplay( $weatherData );
     $display2   =   new  GeneralDisplay( $weatherData );
     $weatherData -> setMeasurements( 20 , 30 , 40 );
     $weatherData -> detach( $display2 );
     print ( " after.../n " );
     $weatherData -> setMeasurements( 33 , 44 , 55 );
?>