Getting An Assertion Failure Error

Question

I am getting the following error when loading one of my views that has a UITableView in it. Does anyone know how to fix it? I have already tried deleting the (void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath method, but that didn't help.

I'm thinking it has to do with the table's delegate not being updated properly with numberOfRowsInSection or something.

*** Assertion failure in -[UITableView _endCellAnimationsWithContext:], /SourceCache/UIKit/UIKit-1448.89/UITableView.m:995
2011-06-05 00:38:12.116 App[14523:707] Serious application error.  An exception was caught from the delegate of NSFetchedResultsController during a call to -controllerDidChangeContent:.  Invalid update: invalid number of rows in section 0.  The number of rows contained in an existing section after the update (5) must be equal to the number of rows contained in that section before the update (5), plus or minus the number of rows inserted or deleted from that section (0 inserted, 3 deleted). with userInfo (null)

Here is my code:

#pragma mark - Table view data source

- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
    return 1;
}

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
    id <NSFetchedResultsSectionInfo> sectionInfo = [[self.fetchedResultsController sections] objectAtIndex:section];
    return [sectionInfo numberOfObjects];
}

-(void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath
{
    if (editingStyle == UITableViewCellEditingStyleDelete) 
    {
        // Delete the managed object for the given index path
        NSManagedObjectContext *context = [self.fetchedResultsController managedObjectContext];
        [context deleteObject:[self.fetchedResultsController objectAtIndexPath:indexPath]];
        NSLog(@"fetched results : \n%@\n",[self.fetchedResultsController fetchedObjects]);

        // Commit the change.
        NSError *error = nil;

        // Update the array and table view.
        if (![managedObjectContext save:&error]) 
        {
            // Handle the error.
        }
        //[tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:YES];
    }
}

#pragma mark - Fetched results controller

- (NSFetchedResultsController *)fetchedResultsController
{
    if (fetchedResultsController != nil)
    {
        return fetchedResultsController;
    }
    // Create the fetch request for the entity.
    NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
    // Edit the entity name as appropriate.
    NSEntityDescription *entity = [NSEntityDescription entityForName:@"Set" inManagedObjectContext:self.managedObjectContext];
    [fetchRequest setEntity:entity];
    [fetchRequest setPredicate:[NSPredicate predicateWithFormat: @"sets == %@", self.exercise]];
    // Set the batch size to a suitable number.
    [fetchRequest setFetchBatchSize:20];
    // Edit the sort key as appropriate.
    NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"timeStamp" ascending:YES];
    NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor, nil];

    [fetchRequest setSortDescriptors:sortDescriptors];

    // Edit the section name key path and cache name if appropriate.
    // nil for section name key path means "no sections".
    NSFetchedResultsController *aFetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:self.managedObjectContext sectionNameKeyPath:nil cacheName:nil];
    aFetchedResultsController.delegate = self;
    self.fetchedResultsController = aFetchedResultsController;

    [aFetchedResultsController release];
    [fetchRequest release];
    [sortDescriptor release];
    [sortDescriptors release];

    NSError *error = nil;
    if (![self.fetchedResultsController performFetch:&error])
    {
        /*
         Replace this implementation with code to handle the error appropriately.

         abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development. If it is not possible to recover from the error, display an alert panel that instructs the user to quit the application by pressing the Home button.
         */
        NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
        abort();
    }
    NSLog(@"fetched results : \n%@\n",[self.fetchedResultsController fetchedObjects]);
    NSLog(@"fetch count: %i", [fetchedResultsController.fetchedObjects count]);
    return self.fetchedResultsController;
}    
#pragma mark - Fetched results controller delegate


- (void)controllerWillChangeContent:(NSFetchedResultsController *)controller
{
    [self.setsTableView beginUpdates];
}

- (void)controller:(NSFetchedResultsController *)controller didChangeSection:(id <NSFetchedResultsSectionInfo>)sectionInfo
           atIndex:(NSUInteger)sectionIndex forChangeType:(NSFetchedResultsChangeType)type
{
    switch(type)
    {
        case NSFetchedResultsChangeInsert:
            [self.setsTableView insertSections:[NSIndexSet indexSetWithIndex:sectionIndex] withRowAnimation:UITableViewRowAnimationFade];
            break;

        case NSFetchedResultsChangeDelete:
            [self.setsTableView deleteSections:[NSIndexSet indexSetWithIndex:sectionIndex] withRowAnimation:UITableViewRowAnimationFade];
            break;
    }
}

- (void)controller:(NSFetchedResultsController *)controller didChangeObject:(id)anObject
       atIndexPath:(NSIndexPath *)indexPath forChangeType:(NSFetchedResultsChangeType)type
      newIndexPath:(NSIndexPath *)newIndexPath
{
    UITableView *tableView = self.setsTableView;

    switch(type)
    {
        case NSFetchedResultsChangeInsert:
            [tableView insertRowsAtIndexPaths:[NSArray arrayWithObject:newIndexPath] withRowAnimation:UITableViewRowAnimationFade];
            break;

        case NSFetchedResultsChangeDelete:
            [tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationFade];
            break;

        case NSFetchedResultsChangeUpdate:
            [self configureCell:[tableView cellForRowAtIndexPath:indexPath] atIndexPath:indexPath];
            break;

        case NSFetchedResultsChangeMove:
            [tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationFade];
            [tableView insertRowsAtIndexPaths:[NSArray arrayWithObject:newIndexPath]withRowAnimation:UITableViewRowAnimationFade];
            break;
    }
}

- (void)controllerDidChangeContent:(NSFetchedResultsController *)controller
{
    [self.setsTableView endUpdates];

    [self.setsTableView reloadData];
}

Answer 1

is Try uncommenting [tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:YES];

Please note:

(NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section

should return a value 1 less than that of before calling 'deleteRows..'

Basic problem is this: You are instructing UI to delete one of the rows, but not removing that row from the back end.

Answer 2

If you are using the code from CoreDataBooks sample you might want to change this:

- (void)addControllerContextDidSave:(NSNotification*)saveNotification {

    NSManagedObjectContext *context = [fetchedResultsController managedObjectContext];
    // Merging changes causes the fetched results controller to update its results
    [context mergeChangesFromContextDidSaveNotification:saveNotification];  
}

with

- (void)addControllerContextDidSave:(NSNotification*)saveNotification {
        double delayInSeconds = 1.0;
        dispatch_time_t popTime = dispatch_time(DISPATCH_TIME_NOW, delayInSeconds * NSEC_PER_SEC);
        dispatch_after(popTime, dispatch_get_main_queue(), ^(void){
            NSManagedObjectContext *context = [fetchedResultsController managedObjectContext];
            // Merging changes causes the fetched results controller to update its results
            [context mergeChangesFromContextDidSaveNotification:saveNotification];
        }); 
    }

This will prevent NSFetchedResultsController from refreshing while the tableView is not visible because of the UINavigationController transition.

Of course this thing occurs only in simulator, because on the device the insert will take longer than the [self dismissModalViewControllerAnimated:YES] animation.

Answer 3

In my case when I called [tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:YES]; only, I got this type of error. I solved this by removing the object from Array (from this array I am displaying data.) and called [tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:YES];

Answer 4

I put each section elements in separated arrays. Then put them into another array( arrayWithArray). My solution here for this problem:

[quarantineMessages removeObject : message];
[_tableView beginUpdates];
if([[arrayWithArray objectAtIndex: indPath.section] count]  > 1)
{
    [_tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indPath] withRowAnimation:UITableViewRowAnimationBottom];
}
else
{
    [_tableView deleteSections:[NSIndexSet indexSetWithIndex:indPath.section]
              withRowAnimation:UITableViewRowAnimationFade];
}
[_tableView endUpdates];