Trying to debug error: *** Assertion failure in -[UITableView _createPreparedCellForGlobalRow:withIndexPath:]

Question

I have a simple UITableviewController that used to work fine and now something has broken it.. It presents a simple form that allows me to add a simple 3-field record to a core-data managed object.

When I add a record, it should return to the table and display the contents. I can see that it is writing the record to the database but the table is empty and the error below appears. I can keep adding records by clicking on my "Add" button but each time I save the new record and return to the table, it is empty.

The complete error I see is this..

*** Assertion failure in -[UITableView _createPreparedCellForGlobalRow:withIndexPath:], /SourceCache/UIKit_Sim/UIKit-1448.89/UITableView.m:5678
2011-10-01 22:48:11.860 Gradetrack[59617:207] Serious application error.  An exception was caught from the delegate of NSFetchedResultsController during a call to -controllerDidChangeContent:.  UITableView dataSource must return a cell from tableView:cellForRowAtIndexPath: with userInfo (null)

If I stop the simulator and restart it, I can see from my NSLog statements that it has discovered the right number of records from the database and has tried to load the table but at this point, I get this similar error and the stack trace below.

2011-10-01 23:08:50.332 Gradetrack[59795:207] >>> Enumber of courses entered thus far: 4 
2011-10-01 23:08:50.334 Gradetrack[59795:207] *** Assertion failure in -[UITableView _createPreparedCellForGlobalRow:withIndexPath:], /SourceCache/UIKit_Sim/UIKit-1448.89/UITableView.m:5678
2011-10-01 23:08:50.337 Gradetrack[59795:207] *** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'UITableView dataSource must return a cell from tableView:cellForRowAtIndexPath:'
*** Call stack at first throw:
(
    0   CoreFoundation                      0x00fd05a9 __exceptionPreprocess + 185
    1   libobjc.A.dylib                     0x01124313 objc_exception_throw + 44
    2   CoreFoundation                      0x00f88ef8 +[NSException raise:format:arguments:] + 136
    3   Foundation                          0x000e43bb -[NSAssertionHandler handleFailureInMethod:object:file:lineNumber:description:] + 116
    4   UIKit                               0x0035ec91 -[UITableView(UITableViewInternal) _createPreparedCellForGlobalRow:withIndexPath:] + 883
    5   UIKit                               0x003544cc -[UITableView(UITableViewInternal) _createPreparedCellForGlobalRow:] + 75
    6   UIKit                               0x003698cc -[UITableView(_UITableViewPrivate) _updateVisibleCellsNow:] + 1561
    7   UIKit                               0x0036190c -[UITableView layoutSubviews] + 242
    8   QuartzCore                          0x01f70a5a -[CALayer layoutSublayers] + 181
    9   QuartzCore                          0x01f72ddc CALayerLayoutIfNeeded + 220
    10  QuartzCore                          0x01f180b4 _ZN2CA7Context18commit_transactionEPNS_11TransactionE + 310
    11  QuartzCore                          0x01f19294 _ZN2CA11Transaction6commitEv + 292
    12  UIKit                               0x002eb9c9 -[UIApplication _reportAppLaunchFinished] + 39
    13  UIKit                               0x002ebe83 -[UIApplication _runWithURL:payload:launchOrientation:statusBarStyle:statusBarHidden:] + 690
    14  UIKit                               0x002f6617 -[UIApplication handleEvent:withNewEvent:] + 1533
    15  UIKit                               0x002eeabf -[UIApplication sendEvent:] + 71
    16  UIKit                               0x002f3f2e _UIApplicationHandleEvent + 7576
    17  GraphicsServices                    0x01928992 PurpleEventCallback + 1550
    18  CoreFoundation                      0x00fb1944 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE1_PERFORM_FUNCTION__ + 52
    19  CoreFoundation                      0x00f11cf7 __CFRunLoopDoSource1 + 215
    20  CoreFoundation                      0x00f0ef83 __CFRunLoopRun + 979
    21  CoreFoundation                      0x00f0e840 CFRunLoopRunSpecific + 208
    22  CoreFoundation                      0x00f0e761 CFRunLoopRunInMode + 97
    23  UIKit                               0x002eb7d2 -[UIApplication _run] + 623
    24  UIKit                               0x002f7c93 UIApplicationMain + 1160
    25  Gradetrack                          0x00002034 main + 102
    26  Gradetrack                          0x00001fc5 start + 53

Based on NSLog statements, this is the last subroutine executed.

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
    // Return the number of rows in the section.
    NSLog(@">>> Enteringg %s [Line %d] ", __PRETTY_FUNCTION__, __LINE__);   

    id <NSFetchedResultsSectionInfo> sectionInfo = 
    [[_fetchedResultsController sections] objectAtIndex:section];
    NSLog(@">>> Enumber of courses entered thus far: %d ", [sectionInfo numberOfObjects]);  

    return [sectionInfo numberOfObjects];
}

Note: the output from the Number of courses entered thus far... was 4, which was correct.

Here is where I return cells back to the UITableViewController

- (UITableViewCell *)tableView:(UITableView *)tableView atIndexPath:(NSIndexPath *)indexPath {
    NSLog(@">>> Entering %s [Line %d] ", __PRETTY_FUNCTION__, __LINE__);    

    static NSString *CellIdentifier = @"Cell";

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

    // Set up the cell...
    [tableView setAllowsSelectionDuringEditing:NO];
    [self configureCell:cell atIndexPath:indexPath];
    // load the cell with an appropriate image
    NSString *path = [[NSBundle mainBundle] pathForResource:@"studentprofile" ofType:@"png"];
    UIImage *theImage = [UIImage imageWithContentsOfFile:path];
    cell.imageView.image = theImage;

    return cell;
}

Based on these errors and my stack trace, can anyone point me in the right direction?

Many thanks,

Phil

Answer 1

I just ran into the same issue, but I carelessly declared:

<UITableViewDelegate, UITableViewDelegate>

rather than correctly:

<UITableViewDelegate, UITableViewDataSource>

Joe

*update - I have also noticed in xCode 4.3 the template generated when you create a new UITableViewController Class is missing a key item in cellForRowAtIndexPath. That is:

    if (cell == nil) {
    cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier];
    cell.accessoryType = UITableViewCellAccessoryDisclosureIndicator;
}