C++ callback 规格严格

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.

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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;  
 
}; 
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.

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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;  
    }  
 
}; 
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:

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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)(a))
{
   std::cout << "CallBack Fired Successfully!" << std::endl;
}
else
{
   std::cout << "CallBack Fired Unsuccessfully!" << std::endl;
}
 

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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;
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;
}
 

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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;  
} 
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;
}
 

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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;  
 
} 
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 (http://www.partow.net/programming/templatecallback/index.html)

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