C++ map of “events” and member function pointers

Question

I\'ve managed to write a template class to work like a callback, learned from the accepted answer of this question How to define a general member function pointer.

I wis

Answer 1

There's no need for inheritance here. Just use std::function to store the member function pointers and std::bind to bind together the member function pointer and the object instance.

#include <functional>
#include <map>
#include <string>
#include <iostream>

struct Apple {
    void Red () {
        std::cout << "aa\n";
    }
};

struct Orange {
    void Blue () {
        std::cout << "bb\n";
    }
};

int main()
{
    std::map<std::string, std::function<void()>> m;
    Apple a;
    Orange o;

    m["apple"] = std::bind(&Apple::Red, a);
    m["orange"] = std::bind(&Orange::Blue, o);

    m["apple"]();
    m["orange"]();
}

Output:

aa
bb

Answer 2

Madness lies, this way: Don't bind callbacks to specific classes. Instead, use a std::function<Signature> object and create suitable function objects: when you need to operate on different classes, you also need to operate on objects of different types. Using a std::function<...> should do the trick, e.g.:

std::map<std::string, std::function<void()>> operations;
operations["talk"] = std::bind(&ChildA::Talk, ChildA());
operations["walk"] = std::bind(&ChildB::Walk, ChildB());
operations["talk"]();