Question

I only ask this question because I have isolated it to pretty much three lines of code, so it’s probably something really obvious that I just screwed up because I’m inexperienced:

Movie* ptr;
if(title == r->getItem().getTitle())
{
    ptr = &(r->getItem());
    cout << "Found: " << ptr->getTitle() << "!";
}

Essentially whats going on is that title == "The Godfather" so therefore that’s what
r->getItem().getTitle() is returning. What I don’t understand though, is that when I try to make a pointer that points to the Movie object returned by r.getItem(), I can’t use the pointer. It definitely had something assigned to it, but when I try to do ptr->getTitle() its returning null.

What on earth is going on?

Answer 1

I think you are doing something like this

Movie& getItem () {
   Movie m ();
   return m;
}

/* ... */

Movie * p = & (getItem ());

The problem is that m is a stack object which gets lost after getItem has returned. That’s a common mistake in C++.

The getTitle call should not work either, but it might by chance.

You must create the object on the heap.

My simple rule to avoid this: Don’t use the & operator altogether unless you haven’t thought about what you are doing ten times.