Question

I ran into a bizarre issue here. I’m developping an iOS app (for iPad, specifically), and I’m using an UITableView at some point to display a list of things.

Now, when I scroll inside the bounds of the view (not above first element, and not below the last), it works okay. However, it just crashes violently when I scroll further than that, with no other messages than :

• EXC_BAD_ACCESS when I scroll down to the last element
• SIGABRT with a backtrace when I scroll upper than the first

I looked on Google, and it seems like I’m releasing some objects too much, but I can’t figure out which ones.

I also tried running the app inside the Instruments, but the Instruments window just freezes each time I run the app, forcing me to kill it by hand… And of course I get no results…

Here a bit of the related code :

    /*
     Returns the cells of the table view
     */
    -(UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
    {
        // Create a new cell view
        static NSString *CellIdentifier = @"Cell";

        UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
        if (cell == nil) {
            cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier] autorelease];
        }

        // Configure the cell...
        cell.textLabel.text = [newestModules objectAtIndex:indexPath.row];
        cell.textLabel.textColor = [UIColor whiteColor];
        cell.backgroundColor = [UIColor colorWithPatternImage: [UIImage imageNamed:@"Background-Texture-Dark-Small.png"]];
        cell.imageView.image = [UIImage imageNamed:@"Icon-Maths.png"];

        UIView *v = [[[UIView alloc] initWithFrame:cell.frame] autorelease];

        // Set view background color
        v.backgroundColor = [UIColor colorWithPatternImage:[UIImage imageNamed:@"Background-Texture-Dark-Small.png"]];

        // This view will be activated when the cell is selected
        cell.selectedBackgroundView = v;

        return cell;
    }

EDIT: UITableView Load and Unload methods :

- (void)viewDidLoad
{
    [super viewDidLoad];

    // Transparent background
    self.tableView.backgroundView = nil;

    // Generate list of newest modules. Will later look for them on the internet, but for now we only add some test examples.
    newestModules = [[NSMutableArray alloc] initWithObjects:@"Test 1", @"Test 2", @"Test 3", @"Test 4", @"Test 5", nil];
}

- (void)viewDidUnload
{
    [newestModules release];
    [super viewDidUnload];
}

Answer 1

It seems that, when you add an object, like a new controller, inside the Interface Builder, it is auto-released by default.

If you don’t link it with a retained property inside a class, it gets released right after its initialization, causing the dreaded EXC_BAD_ACCESS error.