static void checkCollision(GameObject *a, GameObject *b)
{
        // at least one of them should always be a ball.
        if (a->collisionClass == GameObject::BallCollisions) {
                b->checkBallCollision(static_cast <Ball *>(a));
        } 
        if (b->collisionClass == GameObject::BallCollisions) {
                a->checkBallCollision(static_cast <Ball *>(b));
        }
}

void GameManager::handleCollisions()
{
        for (GameObjectList::iterator i = objects.begin(); i != objects.end(); i++) {
                GameObject *a = *i;
                if (a->collisionClass != GameObject::NoCollisions) {
                        for (GameObjectList::iterator j = i+1; j != objects.end(); j++) {
                                GameObject *b = *j;
                                if (b->collisionClass != GameObject::NoCollisions) {
                                        // don't process collisions between scenery and other
                                        // scenery.
                                        if (! ((a->collisionClass == GameObject::ObstacleCollisions) &&
                                                (b->collisionClass == GameObject::ObstacleCollisions))) {
                                                checkCollision(a,b);    
                                        }
                                } 
                        }
                }
        }
}