Question

i’m sorry for the title. I seem to have a problem. I’m just a beginner and i’m sorry if this was asked before.. i couldnt find a straight answer on this one. (when i search class, pointer and child i get results about passing parent or child pointers… i do not want to pass the (this) child or parent pointer, i just want to pass a pointer i initialized on a child class.. to the parent). What i’m trying to do here is better explained by code:

class App
{
public:
    virtual void init(void)         { window = &BasicWindow(); }
    virtual void createWindow(void) { window->create(); }

protected:
    Window *window;
};  

class Game : public App
{
public:
    virtual void init(void)         { window = &OpenGLWindow(); }
};

int main ()
{
    App *game = &Game();
    game->init();
    game->createWindow();
    return 0;
}

Is this legal?
I have an abstract Window class from which BasicWindow and OpenGLWindow derives.
However, when i create the window i get an Access violation reading location error breaking at window->create() inside the App::createWindow() function.

Thanks

Answer 1

I’m guessing this is because you are pointing to a temporary:

window = &BasicWindow()

Once that function exits, window points to “crap” and bad things will happen.

presumably, what you want to do is to create a new instance of the window – i.e.

window = new BasicWindow();

Don’t forget to cleanup!