Question

I’m going through the Beginning iPhone Development book & stuck in chapter 9. I’ve spent a few hours trying to debug this error without avail:

2010-05-01 19:27:51.361 Nav2[4113:20b] *** Assertion failure in -[UITableView _createPreparedCellForGlobalRow:withIndexPath:], /SourceCache/UIKit/UIKit-984.38/UITableView.m:4709
2010-05-01 19:27:51.362 Nav2[4113:20b] *** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'UITableView dataSource must return a cell from tableView:cellForRowAtIndexPath:'
2010-05-01 19:27:51.364 Nav2[4113:20b] Stack: (
 ...
)

I’m not looking for help with the book, but tips for how to debug this error. Can I pin down which of my cellForRowAtIndexPath methods is the problem? And how to inspect the type? Or other things should I look at?

Edit: As requested, the code for the two suspect methods:

-(UITableViewCell *)tableView:(UITableView *)tableView
        cellForRowAtIndexPath:(NSIndexPath *)indexPath {

    static NSString *RootViewControllerCell = @"RootViewControllerCell";

    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:RootViewControllerCell];
    if (cell == nil) {
        cell == [[[UITableViewCell alloc] initWithFrame:CGRectZero reuseIdentifier:RootViewControllerCell] autorelease];
    }

    NSUInteger row = [indexPath row];
    SecondLevelViewController *controller = [controllers objectAtIndex:row];
    cell.textLabel.text = controller.title;
    cell.image = controller.rowImage;
    return cell;
}

—

- (UITableViewCell *)tableView:(UITableView *)tableView 
         cellForRowAtIndexPath:(NSIndexPath *)indexPath {

    static NSString * DisclosureButtonCellIdentifier = 
    @"DisclosureButtonCellIdentifier";

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

    NSUInteger row = [indexPath row];
    NSString *rowString = [list objectAtIndex:row];
    cell.textLabel.text = rowString;
    cell.accessoryType = UITableViewCellAccessoryDetailDisclosureButton;
    [rowString release];
    return cell;
}

Answer 1

You have an extra equals sign, i.e.:

cell == [[[UITableViewCell alloc] initWithFrame:CGRectZero reuseIdentifier:RootViewControllerCell] autorelease];

should be:

cell = [[[UITableViewCell alloc] initWithFrame:CGRectZero reuseIdentifier:RootViewControllerCell] autorelease];