c++ - 如何使 AddCallback() 更安全 - 对象中不同事件的函数

Question

我有 AddCallback()带有第二个参数 int .但是如何减少
传输错误的可能性type从客户端代码？对于这种情况，什么是好的风格？注意: 如果不等于 mouseDown，则类型不正确mouseUp mouseHover mouseLeave

const int  mouseDown = 0;
const int  mouseUp = 1;
const int  mouseHover = 2;
const int  mouseLeave = 3;

class Widget
{
public:
    ...
    bool AddCallback(void (*func)(Widget*), const int type);
protected:
    std::vector<void (*)(Widget*)>  funcsDown;
    std::vector<void (*)(Widget*)>  funcsUp;
    std::vector<void (*)(Widget*)>  funcsHover;
    std::vector<void (*)(Widget*)>  funcsLeave;
    ...
};

Answer 1

对于 C++11，您应该使用强类型枚举:

enum class mouseAction { mouseDown = 0, mouseUp = 1, mouseHover = 2, mouseLeave = 3 };

bool AddCallback(void (*func)(Widget*), const mouseAction type);

使用 C++03，您仍然可以使用枚举并提供第二个重载来使使用整数的调用变成链接器错误:

enum mouseAction { mouseDown = 0, mouseUp = 1, mouseHover = 2, mouseLeave = 3 };

// implement this method (here or somewhere else)
bool AddCallback(void (*func)(Widget*), const mouseAction type);

// but only declare this one:
bool AddCallback(void (*func)(Widget*), const int type);

如果你这样调用它:

myWidget.AddCallback( &foo, mouseDown ); // works
myWidget.AddCallback( &foo, 42 ); // linker error