Can't delete row in section - iphone

Question

i've got a problem by deleting cells in a section.The tableViewController has three sections with various cells. If I try to delete one cell, the debugger will show:
2015-01-23 20:22:15.105 Grade - Zensurenverwaltung[23854:5674475] * Assertion failure in -[UITableView _endCellAnimationsWithContext:], /SourceCache/UIKit_Sim/UIKit-3318.16.14/UITableView.m:1566
2015-01-23 20:22:15.133 Grade - Zensurenverwaltung[23854:5674475] * Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'Invalid update: invalid number of sections. The number of sections contained in the table view after the update (3) must be equal to the number of sections contained in the table view before the update (3), plus or minus the number of sections inserted or deleted (0 inserted, 1 deleted).'
*** First throw call stack:
(
0 CoreFoundation 0x00000001008bef35 exceptionPreprocess + 165
1 libobjc.A.dylib 0x00000001025adbb7 objc_exception_throw + 45
2 CoreFoundation 0x00000001008bed9a +[NSException raise:format:arguments:] + 106
3 Foundation 0x0000000100d565df -[NSAssertionHandler handleFailureInMethod:object:file:lineNumber:description:] + 195
4 UIKit 0x00000001013c98ff -[UITableView _endCellAnimationsWithContext:] + 10935
5 Grade - Zensurenverwaltung 0x00000001000fa0c2 _TFC26Grade___Zensurenverwaltung28TestTypesTableViewController9tableViewfS0_FTCSo11UITableView18commitEditingStyleOSC27UITableViewCellEditingStyle17forRowAtIndexPathCSo11NSIndexPath_T_ + 3618
6 Grade - Zensurenverwaltung 0x00000001000fa207 _TToFC26Grade___Zensurenverwaltung28TestTypesTableViewController9tableViewfS0_FTCSo11UITableView18commitEditingStyleOSC27UITableViewCellEditingStyle17forRowAtIndexPathCSo11NSIndexPath_T_ + 87
7 UIKit 0x00000001013edcb4 -[UITableView animateDeletionOfRowWithCell:] + 130
8 UIKit 0x00000001013ce125 __52-[UITableView _swipeActionButtonsForRowAtIndexPath:]_block_invoke + 72
9 UIKit 0x00000001012f68be -[UIApplication sendAction:to:from:forEvent:] + 75
10 UIKit 0x00000001013fd410 -[UIControl _sendActionsForEvents:withEvent:] + 467
11 UIKit 0x00000001013fc7df -[UIControl touchesEnded:withEvent:] + 522
12 UIKit 0x00000001016a3540 _UIGestureRecognizerUpdate + 9487
13 UIKit 0x000000010133bff6 -[UIWindow _sendGesturesForEvent:] + 1041
14 UIKit 0x000000010133cc23 -[UIWindow sendEvent:] + 667
15 UIKit 0x00000001013099b1 -[UIApplication sendEvent:] + 246
16 UIKit 0x0000000101316a7d _UIApplicationHandleEventFromQueueEvent + 17370
17 UIKit 0x00000001012f2103 _UIApplicationHandleEventQueue + 1961
18 CoreFoundation 0x00000001007f4551 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION + 17
19 CoreFoundation 0x00000001007ea41d __CFRunLoopDoSources0 + 269
20 CoreFoundation 0x00000001007e9a54 __CFRunLoopRun + 868
21 CoreFoundation 0x00000001007e9486 CFRunLoopRunSpecific + 470
22 GraphicsServices 0x00000001052fd9f0 GSEventRunModal + 161
23 UIKit 0x00000001012f5420 UIApplicationMain + 1282
24 Grade - Zensurenverwaltung 0x00000001001e164e top_level_code + 78
25 Grade - Zensurenverwaltung 0x00000001001e168a main + 42
26 libdyld.dylib 0x0000000102d87145 start + 1
27 ??? 0x0000000000000001 0x0 + 1
)
libc++abi.dylib: terminating with uncaught exception of type NSException
And i just don't get it...
Here is my code:
override func tableView(tableView: UITableView, commitEditingStyle editingStyle: UITableViewCellEditingStyle, forRowAtIndexPath indexPath: NSIndexPath) {
var indexes: NSMutableIndexSet = NSMutableIndexSet()
dataTestType = context.executeFetchRequest(fetchRequestForTestType, error: nil) as [TestType]
if editingStyle == UITableViewCellEditingStyle.Delete {
context.deleteObject(dataTestType[indexPath.row] as NSManagedObject)
context.save(nil)
dataTestType.removeAtIndex(indexPath.row)
if dataTestType.count == 0 {
indexes.addIndex(indexPath.section)
}
tableView.beginUpdates()
tableView.deleteRowsAtIndexPaths([indexPath], withRowAnimation: .Fade)
tableView.deleteSections(indexes, withRowAnimation: .Fade)
tableView.endUpdates()
}
}
Can anyone help me?
Thank You very much!

Answer 1

You remove an object at indexPath.row from the dataTestType array
dataTestType.removeAtIndex(indexPath.row)
And on the next line you try to get the object at the same index, but it won't exist if you deleted the only object in the array:
context.deleteObject(dataTestType[indexPath.row] as NSManagedObject)
You can simply solve the issue by reordering these two lines.
As matt pointed out, you can also use NSFetchedResultsController, as it is recommended for showing Core Data records in UITableView. Then you won't need dataTestType array at all. Now you call context.executeFetchRequest each time commitEditingStyle method is called. It is inefficient and can result in poor performance if you have many records to fetch.