#include <iostream>
    #include <vector>
    #include <memory>

    using namespace std;

    class GameObject
    {
    public:
        virtual void onContact(GameObject* otherObject)
        {
            cout << "object met object" << endl;
        }
    };

    class Crate;
    class Wall;
    class Hero;

    class Crate: public GameObject
    {
    public:
        virtual void onContact(Wall* w)
        {
            cout << "crate met wall" << endl;
        }
        virtual void onContact(Hero* h)
        {
            cout << "crate met hero" << endl;
        }
    };

    class Wall: public GameObject
    {
    public:
        virtual void onContact(Crate* c)
        {
            cout << "wall met crate" << endl;
        }
        virtual void onContact(Hero* h)
        {
            cout << "wall met hero" << endl;
        }
    };


    class Hero: public GameObject
    {
    public:
        virtual void onContact(Crate* crate)
        {
            cout << "hero met crate" << endl;
        }
        virtual void onContact(Wall* w)
        {
            cout << "hero met wall" << endl;
        }
    };

    int main()
    {
        //Works
        auto hero = unique_ptr<Hero>(new Hero());
        auto crate = unique_ptr<Crate>(new Crate());
        auto wall = unique_ptr<Wall>(new Wall());

        hero->onContact(crate.get()); // "hero met crate"
        hero->onContact(wall.get()); // "hero met wall"
        crate->onContact(wall.get()); // "crate met wall"
        wall->onContact(crate.get()); // "wall met crate"

        cout << endl;

        //Problem: in the program the game objects are stored in a vector (homogeneous container)
        vector<unique_ptr<GameObject>> gameObjects;
        gameObjects.push_back(move(hero));
        gameObjects.push_back(move(crate));
        gameObjects.push_back(move(wall));

        /*
        "object met object".
        Should be "hero met crate".
        That's because all objects in vector are GameObject.
        */
        gameObjects[0]->onContact(gameObjects[1].get());

        /* "object met object", should be "wall met crate" */
        gameObjects[2]->onContact(gameObjects[1].get());

        return 0;
    }