C++ callbacks

EventHandler.cpp

#include <functional>
class EventHandler
{
    public:
        void addHandler(std::function<void(int)> callback)
        {
            fCallback = callback
        }
        
        void performCallback()
        {
          fCallback(1);
        }
        
    private:
      std::function<void(int)> fCallback;
  
};

MyClass.cpp

class MyClass
{
    public:
        MyClass();

        // Note: No longer marked `static`, and only takes the actual argument
        void Callback(int x);
    private:
        int private_x;
};

MyClass::MyClass()
{
    

    private_x = 5;
    handler->addHandler(std::bind(&MyClass::Callback, this, std::placeholders::_1));
}

void MyClass::Callback(int x)
{
    // No longer needs an explicit `instance` argument,
    // as `this` is set up properly
    cout << x + private_x << endl;
}