NSRangeException exception in NSFetchedResultsChangeUpdate event of NSFetchedResultsController

Question

I have a UITableView that uses an NSFetchedResultsController as data source.

The core data store is updated in multiple background threads

Answer 1

I have now found a solution for my problem. In the case of an update event, there is no need to call

[self.controller objectAtIndexPath:indexPath]

because the updated object is already supplied as the anObject parameter to the -controller:didChangedObject:... delegate.

I have therefore replaced -configureCell:atIndexPath: by a -configureCell:withObject: method that uses the updated object directly. This seems to work without problems.

The code looks now like this:

- (void)configureCell:(UITableViewCell *)cell withObject:(MyManagedObject *)myObj
{
    cell.textLabel.text = myObj.name;
}

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:@"MyCellIdentifier"];
    [self configureCell:cell withObject:[self.controller objectAtIndexPath:indexPath]];
    return cell;
}

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

    switch(type) {
    /* ... */           
    case NSFetchedResultsChangeUpdate:
        [self configureCell:[tableView cellForRowAtIndexPath:indexPath] withObject:anObject];
        break;
    /* ... */           
    }
}