Callback with std::function

//
//  main.cpp
//  callbackWithMemberPointer
//
//  Created by Rizky Herucakra on 7/5/13.
//  Copyright (c) 2013 Rizky Herucakra. All rights reserved.
//

#include <iostream>
#include <functional>

class A{
public:
    void a_callback();

};

void A::a_callback(){
    using namespace std;
    cout << "A::a_callback is called";
}

typedef void (A::*callback_func)();

class B{
    std::function<void ()> callback;

public:
    void do_something();
    void register_callback(std::function<void()> f);

};


void B::register_callback(std::function<void()> f){
    callback = f;
}

void B::do_something(){
    using namespace std;
    cout << "B::do_something called" << endl;
    if (callback) callback();
}



int main(int argc, const char * argv[])
{
    using namespace std;
    A a;
    B b;
    b.register_callback(bind(mem_fn(&A::a_callback), &a));
    b.do_something();
}