Question

Is there some way to allocate memory depending on the type of pointer passed?

Here is my problem: I have a ‘bouncyball’ and ‘hero’ class both inheriting from ‘Actor’. To add a bouncyball, I call:

_actors.push_back(new Bouncyball());

For a hero, it would be:

_actors.push_back(new Hero());

Since _actors is a vector of Actor pointers, it works because of polymorphism. But I want to write a generic method to add new actors to my scene:

unsigned Scene::addActor(Actor * actor){
    this->_actors.push_back(new [something]);
}

Because the parameter can be any derivative of Actor, I don’t know what to allocate memory for… I can work around this with a case statement, but what if I derive other Actors later on?

Answer 1

What is wrong with this:

unsigned Scene::addActor(Actor * actor){
    this->_actors.push_back(actor);
    //what do you want to return? why not make return type as void?
}

Isn’t it actor which you want to add to _actors?

And you can call addActor() as:

scene.addActor(new Bouncyball());
scene.addActor(new Hero());

Make sure that you declare the destructor of Actor as virtual, as most likely you would want to delete derived class objects through the pointer of base type (which is Actor).