2.cpp

#include <iostream>

#include <functional>

class Item;

typedef  std::function<void(int)> Action;

class Item 

{

public:

    explicit Item(int y) : y_(y) {}

    void do_action(int x) { action_(x); }

    Action action_;

    int y_;

};

int main()

{

    Item it1(3);

    Action a = [&it1](int x){ std::cout << "Wert x:  " << x << " Wert y: " << it1.y_ << "\n"; };

    it1.action_ = a;

    it1.do_action(5);

}