具有注册样式，通知程序方法的C ++事件处理程序

问题描述

我在c ++中找到了具有注册样式的事件处理程序代码。 谁能解释一下下面的代码是什么？

#include <algorithm>
#include <functional>
#include <list>

class Button {

    public:
        typedef void (*OnPress)(Button *,void *closure);
    
    private:
        typedef std::pair<OnPress,void*> PressCallBack;
        std::list<PressCallBack> onPress;

        struct Notify:
        public std::binary_function<PressCallBack,Button*,void> {
            void operator()( PressCallBack& c,Button* b) const {
                (*c.first)(b,c.second);
            }
        };

        void NotifyAll(void){
            std::for_each(
                onPress.begin(),onPress.end(),std::bind2nd(Notify(),this)
            );
        }

    public:
        void AddOnButtonPress(OnPress f,void *c){
            onPress.push_back(PressCallBack(f,c));
        }

        void RemoveOnButtonPress(OnPress f,void *c){
            onPress.remove(PressCallBack(f,c));
        }
};

任何评论都会有帮助！！！ 预先感谢！

解决方法

某些地方带有签名的功能：

 void function_name(Button* btn,void* ptrToSomeData);

具有第二个参数（ptrToSomeData）的函数可以通过函数Button :: AddOnButtonPress：添加到事件处理程序列表中。

 Button::AddOnButtonPress(function_name,&SomeData);

当某些对象SomeButton调用功能Button :: NotifyAll（）时，所有添加的功能将按添加顺序被调用。第一个参数将传递给按钮（SomeButton）的指针，第二个参数将是添加时指定的参数。

typedef void (*OnPress)(Button *,void *closure);
//< declare OnPress as pointer to function (pointer to Button,pointer to void) returning void

typedef std::pair<OnPress,void*> PressCallBack;
//< declare pair of 
//< - pointer to function (pointer to Button,pointer to void) returning void
//    and
//< - pointer to void
//This type is used to store the pointer to callback function with the second argument of the function

std::list<PressCallBack> onPress; //< list of saved callbacks

struct Notify:
public std::binary_function<PressCallBack,Button*,void> {
    void operator()( PressCallBack& c,Button* b) const {
          (*c.first)(b,c.second);
    }
};
//< the type Notify - it is functor. It is used this way: 
//  Notify()(callback,this);
//  so
//  it calls callback_function(this,store_pointer_to_some_data)

void NotifyAll(void){
    std::for_each(
        onPress.begin(),onPress.end(),std::bind2nd(Notify(),this)
     );
}
//< for every stored callback:
//   1) create object Notify
//   2) call Notify::operator()(PressCallBack,this)

void AddOnButtonPress(OnPress f,void *c){
    onPress.push_back(PressCallBack(f,c));
}
//< store callback function 'f' and second argument 'c' for the callback function 'f' into onPress list

    void RemoveOnButtonPress(OnPress f,void *c){
        onPress.remove(PressCallBack(f,c));
    }
//< store callback function 'f' with the second argument 'c' from onPress list