[ZZ]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
   
     ;

}
  
    

C++ Callback Solution

原文出处：http://blog.csdn.net/force_eagle/archive/2009/07/14/4347329.aspx