关于成员函数的Command模式的简单实现

看到Fox发表关于 成员函数的消息映射的文章，也忍不住发表的一点自己的观点，希望对大家有所帮助。
其实也就是COMMAND模式的简单实现，看代码吧。
1. XGUIEventHandlerPointer.h

namespace  XGUI
{
     class  EventHandlerSlot
    {
     public :
         virtual   ~ EventHandlerSlot() {};
         virtual   void  execute( const  EventArgs &  args)  =   0 ;
         virtual   void *  getClass()  =   0 ;
    };

    template < typename T >
     class  EventHandlerPointer :
         public  EventHandlerSlot
    {
     public :
        typedef  void  (T:: * EventHandler)( const  EventArgs & );
     public :
        EventHandlerPointer() :
            d_undefined( true ),
            d_object(NULL)
        {}
        EventHandlerPointer(EventHandler func, T *  obj) :
            d_function(func),
            d_object(obj),
            d_undefined( false )
        {}
         virtual   ~ EventHandlerPointer() {}

         void  execute( const  EventArgs &  args)
        {
             if ( ! d_undefined) 
                (d_object ->* d_function)(args);
        }

         void *  getClass()
        {
             return  static_cast < void *> (d_object);
        }

     protected :
        EventHandler    d_function;
        T *                 d_object;
         bool             d_undefined;
    };
}

2. XGUIWidget.h
 

namespace  XGUI
{
     //  
     class  Widget
    {
     public :
        template < typename T >   void  addWidgetEventHandler(WidgetEvent EVENT,  void  (T:: * function)( const  EventArgs & ), T *  obj)
        {
            mWidgetEventHandlers[EVENT].push_back( new  EventHandlerPointer < T > (function,obj));
        }
         void  addWidgetEventHandler(WidgetEvent EVENT, EventHandlerSlot *  function)
                {
            mWidgetEventHandlers[EVENT].push_back( new  EventHandlerPointer < T > (function,obj));
        }
                 bool  Widget::fireWidgetEvent(WidgetEvent EVENT, EventArgs &  args)
                {
                       //  If there are no User defined event handlers we are done.
                       if (mWidgetEventHandlers[EVENT].empty())
                        return   false ;
                    
                       //  Execute registered handlers
                      std::vector < EventHandlerSlot *>*  userEventHandlers  =   & (mWidgetEventHandlers[EVENT]);
                       for (std::vector < EventHandlerSlot *> ::iterator it  =  userEventHandlers -> begin(); it  !=  userEventHandlers -> end();  ++ it )
                       ( * it) -> execute(args);
                    
                       return   true ;
             }
         //  .
    };
}

以上只为部分代码。