Question

I have a list where I store a pointer to a pointer of objects. I have a function where I create pointers to these objects and store their addresses in the list (hence pointer to a pointer). However once this function is done that pointer is no longer valid (the object is but not the pointer because it’s out of scope) so now my pointer to pointer doesn’t work. How do you get around this?

list<Actor**> lst;
void CreateEnemy()
{
    Actor* a = new Actor();

    lst.push_back(&a);
}

int _tmain(int argc, _TCHAR* argv[])
{
    CreateEnemy();
    // at this point the pointer to a pointer stored in lst isn't valid anymore because it went out of scope after CreateEnemy() completed.
}

Answer 1

Here’s a simple example of something you could do based on your comments.

list<unique_ptr<Actor>> lst;

void CreateEnemy()
{
    lst.push_back(unique_ptr<Actor>(new Actor));
}

void KillRandomEnemies()
{
    for (auto& i : lst)
    {
        if (rand() % 100)
            i.reset();
    }
}    

class Projectile
{
public:
    Projectile(unique_ptr<Actor> & a)
        :actor(&a)
    {}

    bool IsTargetDead() const { return !(*actor); }

private:
    unique_ptr<Actor> * actor;
};

int main()
{
    CreateEnemy();
    Projectile proj(lst.front());

    while (something())
    {
        KillRandomEnemies();

        if (proj.IsTargetDead())
            whatever();
    }
}