Do I need to free the memory in this case somehow?

Question

I have a pointer State *state; which is a class that other states inherit from. And I do state = new GameState; Do I need to free the memory here somehow, if I change what the object state points to from GameState to something else?

Answer 1

If what you mean is that State* state does NOT own the object you will need to do something like this:

    // create states
    State* game_state = new GameState();
    State* menu_state = new MenuState();
    // set current state
    State* state = game_state;
    // ... do somethings ...

    // delete states
    delete game_state;
    game_state = nullptr;
    delete menu_state;
    menu_state = nullptr;
    state = nullptr;

If you want to write modern code use:

    // create states
    auto game_state = make_unique<GameState>();
    auto menu_state = make_unique<MenuState>();
    // set current state
    State* state = game_state.get();
    // ... do somethings ...

    // no need to delete states
    state = nullptr;

You could also use a combination of shared_ptr's and weak_ptr's.

If not using smart pointers, you need to call delete on whatever owns the object.

---

If State* state DOES own the object then you need to do:

// create current state
State* state = new GameState();
// ... do somethings ...

// switch state
delete state;
state = new MenuState();

// ... do somethings ...

// delete state
delete state;
state = nullptr;

And with smart pointers:

// create current state
unique_ptr<State> state = make_unique<GameState>();
// ... do somethings ...

// switch state (old state automatically deleted)
state = make_unique<MenuState>();
// ... do somethings ...

// delete state
state = nullptr;