在C++中实现C#的delegate机制

用过C#的朋友都觉得C#的确是个好语言，但有时由于特殊需要，不得不用C++，在C++中要想实现C#中的Thread等也是可行的，不过代码要稍复杂。

以例子来说明：

class   Sdk { public: void   DoSomething();   }; class   client { public: Sdk   m_sdk; void   DoSomething{} { m_sdk.DoSomething(); } void   OnMessage() { // } } 

这个例子比较简单，Sdk用来实现某个功能，client是客户程序，要想在m_sdk做处理的时候能发送通知到client，有几个方法可以实现， 其一是发线程消息，其一是回调，但传统的回调对面向对象的支持并不好，这就是实现delegate的出发点。 下面是一个实现：

class   Delegate { public: virtual   ~Delegate(void){   } virtual   void   operator()(void)   =   0; }; template <typename   C> class   DelegateImpl   :   public   Delegate { private: typedef   void   (C::*F)(void); C*   m_class; F   m_fun; public: DelegateImpl(C*   c,   F   f){   m_class   =   c;   m_fun   =   f;   } virtual   void   operator()(void) { if(m_class) return   (m_class-> *m_fun)(); } }; 

有了上面代码，再稍加修改sdk和client代码就能实现事件通知了：

class   Sdk { public: Delegate*   pEvent; sdk():   pEvent(NULL)   {   } void   DoSomething() { cout < <"opened" < <endl; if(pEvent   !=   NULL) (*pEvent)(   ); } }; class   client { private: Sdk   m_sdk; public: client() { m_sdk.pEvent   =   new   Delegate <client> (this,   OnOpen); } void   DoSomething() { m_sdk.DoSomething(); } void   OnDoSomething() { cout < <"event   fired" < <endl; } } 

上面的实现有不少局限性，事件处理方法的返回值和参数设置不是十分灵活，因此可以用宏定义优代以上代码， 下面给出我的全部代码，请朋友指正。

////////////////////////////////////////////////////////////////////////////delegate 0#define DEFINE_DELEGATE(NAME, R)\class NAME##Delegate\{\public:\virtual ~NAME##Delegate(void){ }\virtual R operator()(void) = 0;\};\template<typename C>\class NAME##DelegateImpl : public NAME##Delegate\{\private:\typedef R (C::*F)(void);\C* m_class;\F m_fun;\public:\NAME##DelegateImpl(C* c, F f){ m_class = c; m_fun = f; }\virtual R operator()(void)\{\if(m_class)\return (m_class->*m_fun)();\}\};\template<typename C, typename F>\NAME##Delegate* Make##NAME##Delegate(C* c, F f)\{\return new NAME##DelegateImpl<C>(c, f);\}////////////////////////////////////////////////////////////////////////////delegate 1#define DEFINE_DELEGATE(NAME, R, P1)\class NAME##Delegate\{\public:\virtual ~NAME##Delegate(void){ }\virtual R operator()(P1 p1) = 0;\};\template<typename C>\class NAME##DelegateImpl : public NAME##Delegate\{\private:\typedef R (C::*F)(P1);\C* m_class;\F m_fun;\public:\NAME##DelegateImpl(C* c, F f){ m_class = c; m_fun = f; }\virtual R operator()(P1 p1)\{\if(m_class)\return (m_class->*m_fun)(p1);\}\};\template<typename C, typename F>\NAME##Delegate* Make##NAME##Delegate(C* c, F f)\{\return new NAME##DelegateImpl<C>(c, f);\}////////////////////////////////////////////////////////////////////////////delegate 2#define DEFINE_DELEGATE(NAME, R, P1, P2)\class NAME##Delegate\{\public:\virtual ~NAME##Delegate(void){ }\virtual R operator()(P1 p1, P2 p2) = 0;\};\template<typename C>\class NAME##DelegateImpl : public NAME##Delegate\{\private:\typedef R (C::*F)(P1, P2);\C* m_class;\F m_fun;\public:\NAME##DelegateImpl(C* c, F f){ m_class = c; m_fun = f; }\virtual R operator()(P1 p1, P2 p2)\{\if(m_class)\return (m_class->*m_fun)(p1, p2);\}\};\template<typename C, typename F>\NAME##Delegate* Make##NAME##Delegate(C* c, F f)\{\return new NAME##DelegateImpl<C>(c, f);\}/*////////////////////////////////////////////////////////////////////////////sampleDEFINE_DELEGATE(Open, void, int, string)class sdk{public:OpenDelegate* pEvent;sdk(): pEvent(NULL) { }void Open(){cout<<"opened"<<endl;if(pEvent != NULL)(*pEvent)(100, "你好");}};class client{private:sdk m_sdk;public:client(){m_sdk.pEvent = MakeOpenDelegate(this, OnOpen2);}void Open(){m_sdk.Open();}void OnOpen(){cout<<"Open event fired"<<endl;}void OnOpen2(int t, string str){cout<<"Open event fired, Param = "<<t<<"param2 = "<<str.c_str()<<endl;}};*/