C++中回调的使用方法
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;
}
补充:软件开发 , C++ ,