Question

I have a class hierarchy as such:

Entity  
    Stationary  
        Tree  
    Creature  
        Bear  
        Crow  

And I have a World and a Player. When the Player bumps into something it gets a call to handleCollision(Entity* entity) and then depending on what it is different things happen; if the player bumps into a tree nothing happens while the player attack if it’s a bear. The problem is that I’m not sure how to differentiate between cases in a good way.

One thought that has come to mind is someting like this. Player::handleCollision(Entity*) calls Entity->handleCollisionHelper(Player& ). This is a virtual function which in Tree does nothing and in Creature(it should attack all creatures) calls Player.handleCollisionCreature(this) and then place the attack code in handleCollisionCreature. Is there a better way to do this without using RTTI (typeid etc)?

Answer 1

The virtual method with (Player& player) arg seems perfectly good OO design. As you said, you could add some form of type or use RTTI and switch case through the permutations but that would be very C style functional style. Just as long as you aren’t making thousands of virtual calls per second you should be fine.