how to implement callback system

0
votes

I am trying to implement a class system that uses callbacks to notify of certain events. I can think of 2 ways to do this:

#include <functional>
#include <iostream>

class A {
public:
    A(std::function<void(int)>&& func) : f(std::move(func)) {}
    void run() { f(2); }
    std::function<void(int)> f;
};

template <class F>
class B {
public:
    B(F&& func) : f(std::move(func)) {}
    void run() { f(2); }
    F f;
};

int main() {
    int n = 1;
    A a1([n](int b){std::cout << n+b << '\n';});
    B b1([n](int b){std::cout << n+b << '\n';});
    a1.run();
    b1.run();
}

What are the advantages/disadvantages of using these 2 approaches (having a template type for the callback type vs. using std::function)

c++