C++中回调(CallBack)的使用方法

回调函数是一个很有用，也很重要的概念。当发生某种事件时，系统或其他函数将会自动调用你定义的一段函数。回调函数在windows编程使用的场合很多，比如Hook回调函数：MouseProc,GetMsgProc以及EnumWindows,DrawState的回调函数等等，还有很多系统级的回调过程。 一般情况下, 我们使用的回调函数基本都是采用C语言风格. 这里介绍一种C++风格的回调对象方法. 采用template实现.

template < class Class, typename ReturnType, typename Parameter > class SingularCallBack { public: typedef ReturnType (Class::*Method)(Parameter); SingularCallBack(Class* _class_instance, Method _method) { //取得对象实例地址,及调用方法地址 class_instance = _class_instance; method = _method; }; ReturnType operator()(Parameter parameter) { // 调用对象方法 return (class_instance->*method)(parameter); }; ReturnType execute(Parameter parameter) { // 调用对象方法 return operator()(parameter); }; private: Class* class_instance; Method method; };

示例:

以下是两个类实现.

class A { public: void output() { std::cout << "I am class A :D" << std::endl; }; }; class B { public: bool methodB(A a) { a.output(); return true; } };

SingularCallBack的各种调用示例:

A a; B b; SingularCallBack< B,bool,A >* cb; cb = new SingularCallBack< B,bool,A >(&b,&B::methodB); if((*cb)(a)) { std::cout << "CallBack Fired Successfully!" << std::endl; } else { std::cout << "CallBack Fired Unsuccessfully!" << std::endl; }

A a; B b; SingularCallBack< B,bool,A >* cb; cb = new SingularCallBack< B,bool,A >(&b,&B::methodB); if(cb->execute(a)) { std::cout << "CallBack Fired Successfully!" << std::endl; } else { std::cout << "CallBack Fired Unsuccessfully!" << std::endl; }

A a; B b; SingularCallBack< B,bool,A >cb(&b,&B::methodB); if(cb(a)) { std::cout << "CallBack Fired Successfully!" << std::endl; } else { std::cout << "CallBack Fired Unsuccessfully!" << std::endl; }

class AClass { public: AClass(unsigned int _id): id(_id){}; ~AClass(){}; bool AMethod(std::string str) { std::cout << "AClass[" << id << "]: " << str << std::endl; return true; }; private: unsigned int id; }; typedef SingularCallBack < AClass, bool, std::string > ACallBack; int main() { std::vector < ACallBack > callback_list; AClass a1(1); AClass a2(2); AClass a3(3); callback_list.push_back(ACallBack(&a1, &AClass::AMethod)); callback_list.push_back(ACallBack(&a2, &AClass::AMethod)); callback_list.push_back(ACallBack(&a3, &AClass::AMethod)); for (unsigned int i = 0; i < callback_list.size(); i++) { callback_list[i]("abc"); } for (unsigned int i = 0; i < callback_list.size(); i++) { callback_list[i].execute("abc"); } return true; }

引用:

C++ Callback Solution