Row -1 or NSUIntegerMax Given by -[UITableViewDelegate tableView:titleForDeleteConfirmationButtonForRowAtIndexPath:] - ios

Question

Under what circumstances do UITableView give -1 or NSUIntegerMax for the row in -[UITableViewDelegate tableView:titleForDeleteConfirmationButtonForRowAtIndexPath:]?
Below it is a crash log form an user.
OS Version: iPhone OS 9.2.1 (13D15)
Application Specific Information:
*** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'no object at index 18446744073709551615 in section at index 0'
Last Exception Backtrace:
0 CoreFoundation 0x0000000181241900 __exceptionPreprocess + 124
1 libobjc.A.dylib 0x00000001808aff80 objc_exception_throw + 56
2 CoreData 0x0000000182cc50bc -[NSFetchedResultsController objectAtIndexPath:] + 456
3 My App 0x000000010022c678 -[MyViewController tableView:titleForDeleteConfirmationButtonForRowAtIndexPath:] (MyViewController.m:560)
4 UIKit 0x0000000186145174 -[UITableView _titleForDeleteConfirmationButtonForRowAtIndexPath:] + 160
5 UIKit 0x00000001862756f4 -[UITableView _deleteConfirmationButtonForRowAtIndexPath:] + 116
6 UIKit 0x0000000186275cf4 -[UITableView _swipeActionButtonsForRowAtIndexPath:] + 824
7 UIKit 0x0000000186275998 -[UITableView _swipeActionButtons] + 92
8 UIKit 0x0000000186144bd8 __32-[UITableViewCell _beginSwiping]_block_invoke + 120
9 UIKit 0x0000000185f42964 +[UIView(Animation) performWithoutAnimation:] + 80
10 UIKit 0x0000000186144b48 -[UITableViewCell _beginSwiping] + 96
11 UIKit 0x0000000186272320 -[UITableViewWrapperView handleSwipeBeginning:] + 256
12 UIKit 0x00000001864b4ea4 _UIGestureRecognizerSendTargetActions + 396
13 UIKit 0x00000001860d85b8 _UIGestureRecognizerSendActions + 172
14 UIKit 0x0000000185f669b0 -[UIGestureRecognizer _updateGestureWithEvent:buttonEvent:] + 784
15 UIKit 0x00000001864b63bc ___UIGestureRecognizerUpdate_block_invoke904 + 72
16 UIKit 0x0000000185f25b58 _UIGestureRecognizerRemoveObjectsFromArrayAndApplyBlocks + 372
17 UIKit 0x0000000185f228dc _UIGestureRecognizerUpdate + 2404
18 UIKit 0x0000000185f64820 -[UIWindow _sendGesturesForEvent:] + 1132
19 UIKit 0x0000000185f63e1c -[UIWindow sendEvent:] + 764
20 UIKit 0x0000000185f344cc -[UIApplication sendEvent:] + 248
21 UIKit 0x0000000185f32794 _UIApplicationHandleEventQueue + 5528
22 CoreFoundation 0x00000001811f8efc __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__ + 24
23 CoreFoundation 0x00000001811f8990 __CFRunLoopDoSources0 + 540
24 CoreFoundation 0x00000001811f6690 __CFRunLoopRun + 724
25 CoreFoundation 0x0000000181125680 CFRunLoopRunSpecific + 384
26 GraphicsServices 0x0000000182634088 GSEventRunModal + 180
27 UIKit 0x0000000185f9cd90 UIApplicationMain + 204
28 My App 0x00000001000a926c main (main.m:16)
29 ??? 0x0000000180cc68b8 0x0 + 0
- (NSString *)tableView:(UITableView *)tableView titleForDeleteConfirmationButtonForRowAtIndexPath:(NSIndexPath *)indexPath
{
MyMessage *message = [self messageAtIndex:indexPath.row];
if ([message.senderUid isEqualToString:mUid])
return NSLocalizedString(#"Delete", nil);
else
return NSLocalizedString(#"Hide", nil);
}
- (MyMessage *)messageAtIndex:(NSInteger)index
{
return [mMessagesController objectAtIndexPath:[NSIndexPath indexPathForRow:index inSection:0]];
}

Answer 1

indexPath.row and indexPath.section are each a NSUInteger (unsigned integer), which means that it's strictly positive. If you subtract and end up going negative, it jumps up to NSUIntegerMax. This makes it necessary to be careful with arithmetic involving index paths.
When you do row - 1 for row equal to zero, you will get NSUIntegerMax.

Answer 2

I guess the answer is: under no circumstance. If you're cell would be out of bounds the crash would display on rendering time, not when accessing [UITableViewDelegate tableView:titleForDeleteConfirmationButtonForRowAtIndexPath:]
So the issue has to do with trying to retrieve an object from mMessagesController. Try using:
- (MyMessage *)messageAtIndex:(NSInteger)index
{
return [[mMessagesController fetchedObjects] objectAtIndexPath:[NSIndexPath indexPathForRow:index inSection:0]];
}
or
- (MyMessage *)messageAtIndex:(NSInteger)index
{
return [mMessagesController objectAtIndex:index];
}
In Addition you could also filter the call to messageAtIndex to avoid going out of bounds.
- (NSString *)tableView:(UITableView *)tableView titleForDeleteConfirmationButtonForRowAtIndexPath:(NSIndexPath *)indexPath
{
if (indexPath.row < [mMessagesController fetchedObjects].count && indexPath.row >= 0) {
MyMessage *message = [self messageAtIndex:indexPath.row];
if ([message.senderUid isEqualToString:mUid])
return NSLocalizedString(#"Delete", nil);
else
return NSLocalizedString(#"Hide", nil);
} else {
return NSLocalizedString(#"Error", nil);
}
}

Answer 3

It is an iOS bug. Apple marked my bug as a duplicate of 23821434.