repos/Callback_05/Callback_05.cpp

#include <iostream>
#include <functional>

using std::cout;
using std::endl;

class EventHandler
{
public:
/*
    template<typename T>
    void addHandler(T* owner)
    {
        cout << "Handler added..." << endl;
        //Let's pretend an event just occured
        owner->Callback(owner, 1);
    }
*/
    void addHandler(std::function<void(int)> callback)
    {
        cout << "Handler added..." << endl;
        // Let's pretend an event just occured
        callback(1);
    }

};

EventHandler* handler;

/**********************************************************************************************
 *
 */

class MyClass
{
public:
    MyClass() {
        using namespace std::placeholders;

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

    void Callback(int x) {
        cout << x + private_x << endl;
    }
    
    int public_x = 12;
private:
    int private_x;
};

/**********************************************************************************************
 *
 */

class YourClass
{
public:
    YourClass()
    {
        using namespace std::placeholders;

        private_y = 8;
        handler->addHandler(std::bind(&YourClass::Callback, this, _1));
    }

    void Callback(int x) 
    {
        cout << x + private_y << endl;
    }

private:
    int private_y;
};

/**********************************************************************************************
 * 
 */

void freeStandingCallback(int x)
{
    cout << x << endl;
}

/**********************************************************************************************
 *
 */

// https://en.cppreference.com/w/cpp/language/function_template

template<class X>
void f(X a) {
    printf("Test");
}

template<class X>
void f(X* a) {
    printf("Test");
}

void (*p)(int*) = &f;

// https://en.cppreference.com/w/cpp/language/function_template

// template<class T1, class T2>
void g(MyClass* a1, YourClass* a2) {

    printf("access both classes\n"); 
    printf("MyClass: %d\n", a1->public_x);
    printf("YourClass: private\n");
}



int main(int argc, char** argv)
{
    handler = new EventHandler();
    MyClass* myClass = new MyClass();
    YourClass* yourClass = new YourClass();

    handler->addHandler([](int x) { 
        std::cout << "x is " << x << '\n'; 
        });

    handler->addHandler(freeStandingCallback);

    f(myClass->public_x);

    g(myClass, yourClass);

}