NSRangeException-索引（2008）超出范围（1）

Question

I am trying to get the contents of my UITableViewCell before I delete it from my Core Data model in order to act on its contents. If there is only one item in the Core Data model and I go to delete it from my UITableView, the app will only sometimes throw an error of 2014-01-05 11:10:26.189 Nibbles[43609:70b] *** Terminating app due to uncaught exception 'NSRangeException', reason: '*** -[_PFArray objectAtIndex:]: index (2008) beyond bounds (1)'

My biggest confusion is that this only happens with one item in the UITableView and doesn't happen 100% of the time. If you need to see any other code, please let me know.

Here is the code I am using. The bolded line is the one causing the error since it never makes it past there to NSLog to the console.

// Override to support editing the table view.
- (void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath
{
    if (editingStyle == UITableViewCellEditingStyleDelete) {
        NSLog(@"Delete button pressed!");
        FoodListCell *cell = (FoodListCell*)[tableView cellForRowAtIndexPath:indexPath];
        NSLog(@"DEBUG | Selected Cell: %@", cell);

        NSString *foodOrActivity = cell.foodNameLabel.text;
        NSString *points = cell.foodPointsLabel.text;

        NSManagedObjectContext *localContext = [NSManagedObjectContext MR_contextForCurrentThread];
        [[self.fetchedResultsController objectAtIndexPath:indexPath] MR_deleteInContext:localContext];
        [localContext MR_saveOnlySelfAndWait];

        NSIndexPath *path = [NSIndexPath indexPathForRow:indexPath.row inSection:0];
        NSManagedObject *deleteObject = [_fetchedResultsController objectAtIndexPath:path];
        [managedObjectContext deleteObject:deleteObject];
    }

And here is the full stack trace:

2014-01-05 11:10:26.189 Nibbles[43609:70b] *** Terminating app due to uncaught exception 'NSRangeException', reason: '*** -[_PFArray objectAtIndex:]: index (2008) beyond bounds (1)'
*** First throw call stack:
(
    0   CoreFoundation                      0x01cd45e4 __exceptionPreprocess + 180
    1   libobjc.A.dylib                     0x01a578b6 objc_exception_throw + 44
    2   CoreFoundation                      0x01cd43bb +[NSException raise:format:] + 139
    3   CoreData                            0x00280755 -[_PFArray objectAtIndex:] + 133
    4   CoreData                            0x002f9778 -[_PFMutableProxyArray objectAtIndex:] + 120
    5   CoreData                            0x00382c1f -[NSFetchedResultsController objectAtIndexPath:] + 255
    6   Nibbles                             0x0000660d -[FoodListViewController tableView:commitEditingStyle:forRowAtIndexPath:] + 685
    7   UIKit                               0x008b5ba3 -[UITableView animateDeletionOfRowWithCell:] + 107
    8   UIKit                               0x00a35695 -[UITableViewCell _swipeDeleteButtonPushed] + 70
    9   libobjc.A.dylib                     0x01a69874 -[NSObject performSelector:withObject:withObject:] + 77
    10  UIKit                               0x007c70c2 -[UIApplication sendAction:to:from:forEvent:] + 108
    11  UIKit                               0x007c704e -[UIApplication sendAction:toTarget:fromSender:forEvent:] + 61
    12  UIKit                               0x008bf0c1 -[UIControl sendAction:to:forEvent:] + 66
    13  UIKit                               0x008bf484 -[UIControl _sendActionsForEvents:withEvent:] + 577
    14  UIKit                               0x008be733 -[UIControl touchesEnded:withEvent:] + 641
    15  UIKit                               0x00b39c7f _UIGestureRecognizerUpdate + 7166
    16  UIKit                               0x0080419a -[UIWindow _sendGesturesForEvent:] + 1291
    17  UIKit                               0x008050ba -[UIWindow sendEvent:] + 1030
    18  UIKit                               0x007d8e86 -[UIApplication sendEvent:] + 242
    19  UIKit                               0x007c318f _UIApplicationHandleEventQueue + 11421
    20  CoreFoundation                      0x01c5d83f __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__ + 15
    21  CoreFoundation                      0x01c5d1cb __CFRunLoopDoSources0 + 235
    22  CoreFoundation                      0x01c7a29e __CFRunLoopRun + 910
    23  CoreFoundation                      0x01c79ac3 CFRunLoopRunSpecific + 467
    24  CoreFoundation                      0x01c798db CFRunLoopRunInMode + 123
    25  GraphicsServices                    0x0285e9e2 GSEventRunModal + 192
    26  GraphicsServices                    0x0285e809 GSEventRun + 104
    27  UIKit                               0x007c5d3b UIApplicationMain + 1225
    28  Nibbles                             0x000236ad main + 141
    29  libdyld.dylib                       0x031b470d start + 1
)
libc++abi.dylib: terminating with uncaught exception of type NSException

Answer 1

The conventional pattern is to access the model (not through a table cell, but directly from the model). Do whatever you need to do with it, then remove it from your model, then remove it from your table...

The error implies that the localContext being accessed this method is different from (or is in a different state than) the MOC that reports the number of items in the model (used in numberOfRowsInSection :)

Before moving on to recording that deleted object's state, or deleting it. Fix the code that gets that object and just NSLog it. The code that gets that object should exactly match the code that gets it in your cellForRowAtIndexPath :, and the MOC used there should exactly match the numberOfRowsInSection : MOC.

Answer 2

NSIndexPath *path = [NSIndexPath indexPathForRow:indexPath.row inSection:0];
NSManagedObject *deleteObject = [_fetchedResultsController objectAtIndexPath:path];
[managedObjectContext deleteObject:deleteObject];

Here you are getting the index path for the row in section 0 and deleting it.

You already have the index path for the row/cell/section that you want to delete, so why are you trying to delete that row only in section 0?

Try a breakpoint at this line and add some logging to show what row in section 0 is trying to be deleted.