Question

I am not sure how to approach this problem:

‘Player’ class maintains a list of Bullet* objects:

class Player
{
protected:
    std::list< Bullet* > m_pBullet_list;
}

When the player fires a Bullet, it is added to this list. Also, inside the constructor of bullet, a reference of the same object is updated in CollisionMgr, where CollisionMgr also mantains a list of Bullet*.

Bullet::Bullet(GameGL*a_pGameGL, Player*a_pPlayer)
: GameObject( a_pGameGL )
{      
    m_pPlayer = a_pPlayer;

    m_pGameGL->GetCollisionMgr()->AddBullet(this);
}

---

class CollisionMgr
{

void AddBullet(Bullet* a_pBullet);

protected:
std::list< Bullet*> m_BulletPList;
}

---

In CollisionMgr.Update(); based on some conditions, I populate class Cell which again contain a list of Bullet*. Finally, certain conditions qualify a Bullet to be deleted. Now, these conditions are tested upon while iterating through a Cell’s list. So, if I have to delete the Bullet object, from all these places, how should I do it so that there are no more dangling references to it?

std::list< Bullet*>::iterator bullet_it;

    for( bullet_it = (a_pCell->m_BulletPList).begin(); bullet_it != (a_pCell->m_BulletPList).end(); bullet_it++) {

        bool l_Bullet_trash = false;
        Bullet* bullet1 = *bullet_it;

        // conditions would set this to true

        if ( l_Bullet_Trash )
            // TrashBullet( bullet1 );
            continue;
        }

---

Also, I was reading about list::remove, and it mentions that it calls the destructor of the object we are trying to delete. Given this info, if I delete from one list, the object does not exist, but the list would still contain a reference to it..How do I handle all these problems?

Answer 1

You are not storing bullets in these lists, but pointers to bullets, so no destructor will be called. The objects can be safely removed from all lists, but you will need to call delete yourself.