Question about Pagecontrol sample app

Question

Hi,
I've been looking at some sample apps to help with a beginners project that I'm doing. There is a Apple sample app for PageControl.
The app delegate contains this code (I hope I'm OK to include this here, please tell if not)
// replace the placeholder if necessary
MyViewController *controller = [viewControllers objectAtIndex:page];
if ((NSNull *)controller == [NSNull null]) {
controller = [[MyViewController alloc] initWithPageNumber:page];
[viewControllers replaceObjectAtIndex:page withObject:controller];
[controller release];
// add the controller's view to the scroll view
if (nil == controller.view.superview) {
CGRect frame = scrollView.frame;
frame.origin.x = frame.size.width * page;
frame.origin.y = 0;
controller.view.frame = frame;
[scrollView addSubview:controller.view];
I've highlighted two lines and my question is: how can controller be used when it has already been released in the previous section?
I'm very new to this and I thought that releaseing an object meant that you could no longer get to it?
Many Thanks in advance
Ziximo
Message was edited by: Ziximo

Answer 1

Objects aren't deallocated until their retain count goes to zero. When the controller is alloced its retain count is one. When the controller is added to the array its retain count is incremented to two. It's then released to reduce the count to one. Assuming the controller isn't retained by any other object, it will be dealloced when it's removed from (and thus released by) the array. - Ray