Question

I am trying to figure out how to pass a UIImage around between various view controllers without duplicating the UIImage and increasing memory unnecessarily. The image is passed successfully using the method below, but I cannot seem to free up this UIImage later on, which ends up weighing down my app with 7MB+ of data that cannot be accounted for. What I want to know is, what is happening to memory when I pass a UIImage (belonging to my current view controller) to a view controller I will be switching to next, and then release the original pointer? Like this:

-(IBAction)startEditing:(id)sender
{

    EditViewController *controller = [[EditViewController alloc] initWithNibName:@"EditViewController" bundle:nil];
    controller.delegate = self;

            //imageDataPhoto1 is of type UIImage (from camera)
            controller.editPhotoData1 = imageDataPhoto1;
            [imageDataPhoto1 release];
            imageDataPhoto1 = nil;

        controller.modalTransitionStyle = UIModalTransitionStyleCrossDissolve;
    [self presentModalViewController:controller animated:YES];

    [controller release];

}

is the DATA of the pointer imageDataPhoto1 not getting released due to it being assigned to the view controller instance before it is released?

Answer 1

If your EditViewController‘s .h file declares the editPhotoData1 @property with retain, then it will automatically retain any object assigned to it. You’ll need to release the object explicitly, at the very least ,in EditViewController‘s dealloc method.

As a matter of course, you should make sure to release any properties set to retain in your dealloc method, for all classes, i.e.:

- (void)dealloc
{
    [editPhotoData1 release];
    ...
    [super dealloc];
}