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。