Question

I am going over my code and trying to get a handle on proper memory management. This code:

imageView = [[[UIImageView alloc] initWithImage:myImage] autorelease];

Causes my application to crash. I am using multiple view controllers within a nav bar controller. The app works fine: I can select a person from the first view controller (tableview) and it puts me to a list of that persons photos, I can then select a photo from that view controller (tableview) and move to a final view with a scrollview for viewing the photo. Once I hit back on the navbar the previous view loads (list of photos in a tableview) however the app crashes right before the row is deselected using this code:

- (void)viewDidAppear:(BOOL)animated {
    [super viewDidAppear:animated];  
    if(RowSelected != nil)
    {
        [MainTableView deselectRowAtIndexPath:RowSelected animated:YES];
    }
}

The selected row is stored when a the user clicks a row.

If I leave the code as:

imageView = [[UIImageView alloc] initWithImage:myImage];

The app runs fine. Am I doing something wrong? Do I not need to autorelease this?

Answer 1

Make sure you create that view in your view controller’s -loadView or -viewDidLoad, not in its initializer. When the controller’s view goes offscreen it usually gets released, which in turn releases its subviews; thus, you should not expect your reference to imageView to remain valid. If you for some reason need the image view to stay in memory even when the view controller’s offscreen, then it’s okay not to call -autorelease when you create it; just make sure to call [imageView release]; in your controller’s -dealloc.