Swift Application crashes due to RLMException - swift

Question

I'm currently writing a programm which will be the final project in my major, "Computer Sciences". The application I'm making is written is Swift. It is basically an application which allows to write and classify the tasks that an user planned to do daily, monthly or yearly. I just got stuck in the debug console. I am unable to figure it out.
I asked to most of my classmates if they could help me out trying to understand from where the issue could from.
The issue might be from the searchBar functionality which is written through the following code:
extension CategoryViewController: SwipeTableViewCellDelegate {
func tableView(_ tableView: UITableView, editActionsForRowAt indexPath: IndexPath, for orientation: SwipeActionsOrientation) -> [SwipeAction]? {
guard orientation == .right else { return nil }
let deleteAction = SwipeAction(style: .destructive, title: "Delete") { action, indexPath in
// handle action by updating model with deletion
if let categoryForDeletion = self.categories?[indexPath.row] {
do {
try self.realm.write {
self.realm.delete(categoryForDeletion)
}
} catch {
print("Error deleting the category, \(error)")
}
}
}
// customize the action appearance
deleteAction.image = UIImage(named: "delete-icon")
return [deleteAction]
}
func collectionView(_ collectionView: UICollectionView, editActionsOptionsForItemAt indexPath: IndexPath, for orientation: SwipeActionsOrientation) -> SwipeOptions {
var options = SwipeOptions()
options.expansionStyle = .destructive
return options
}
}
I got the issue:
'RLMException', reason: 'Index 2 is out of bounds (must be less than 2).'
*** First throw call stack:
(
0 CoreFoundation 0x000000010519e1bb __exceptionPreprocess + 331
1 libobjc.A.dylib 0x00000001038e6735 objc_exception_throw + 48
2 Realm 0x00000001028b4d3e _Z20RLMThrowResultsErrorP8NSString + 670
3 Realm 0x00000001028b5fa6 _ZL25translateRLMResultsErrorsIZ28-[RLMResults objectAtIndex:]E3$_6EDaOT_P8NSString + 118
4 Realm 0x00000001028b5ece -[RLMResults objectAtIndex:] + 110
5 RealmSwift 0x0000000101ef2e3c $S10RealmSwift7ResultsCyxSicig + 220
6 Todoey2 0x0000000101aea48f $S7Todoey222CategoryViewControllerC05tableC0_19editActionsForRowAt3forSay12SwipeCellKit0L6ActionCGSgSo07UITableC0C_10Foundation9IndexPathVAG0lG11OrientationOtFyAI_APtcfU_ + 303
7 Todoey2 0x0000000101aea8e2 $S7Todoey222CategoryViewControllerC05tableC0_19editActionsForRowAt3forSay12SwipeCellKit0L6ActionCGSgSo07UITableC0C_10Foundation9IndexPathVAG0lG11OrientationOtFyAI_APtcfU_TA + 18
8 SwipeCellKit 0x000000010224c3e8 $S12SwipeCellKit0A10ControllerC7perform6action4hideyAA0A6ActionC_SbtF + 776
9 SwipeCellKit 0x0000000102245d99 $S12SwipeCellKit0A10ControllerC7perform6actionyAA0A6ActionC_tF + 1241
10 SwipeCellKit 0x000000010224b734 $S12SwipeCellKit0A10ControllerC16swipeActionsView_9didSelectyAA0afG0C_AA0A6ActionCtF + 52
11 SwipeCellKit 0x000000010224e199 $S12SwipeCellKit0A10ControllerCAA0A19ActionsViewDelegateA2aDP05swipeeF0_9didSelectyAA0aeF0C_AA0A6ActionCtFTW + 9
12 SwipeCellKit 0x000000010222c40e $S12SwipeCellKit0A11ActionsViewC12actionTapped6buttonyAA0A12ActionButtonC_tF + 590
13 SwipeCellKit 0x000000010222c47c $S12SwipeCellKit0A11ActionsViewC12actionTapped6buttonyAA0A12ActionButtonC_tFTo + 60
14 UIKitCore 0x000000010d233ecb -[UIApplication sendAction:to:from:forEvent:] + 83
15 UIKitCore 0x000000010cc6f0bd -[UIControl sendAction:to:forEvent:] + 67
16 UIKitCore 0x000000010cc6f3da -[UIControl _sendActionsForEvents:withEvent:] + 450
17 UIKitCore 0x000000010cc6e31e -[UIControl touchesEnded:withEvent:] + 583
18 UIKitCore 0x000000010ce07018 _UIGestureEnvironmentSortAndSendDelayedTouches + 5387
19 UIKitCore 0x000000010ce00fd1 _UIGestureEnvironmentUpdate + 1506
20 UIKitCore 0x000000010ce009ad -[UIGestureEnvironment _deliverEvent:toGestureRecognizers:usingBlock:] + 478
21 UIKitCore 0x000000010ce0071d -[UIGestureEnvironment _updateForEvent:window:] + 200
22 UIKitCore 0x000000010d27078a -[UIWindow sendEvent:] + 4058
23 UIKitCore 0x000000010d24e394 -[UIApplication sendEvent:] + 352
24 UIKitCore 0x000000010d3235a9 __dispatchPreprocessedEventFromEventQueue + 3054
25 UIKitCore 0x000000010d3261cb __handleEventQueueInternal + 5948
26 CoreFoundation 0x0000000105103721 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__ + 17
27 CoreFoundation 0x0000000105102f93 __CFRunLoopDoSources0 + 243
28 CoreFoundation 0x00000001050fd63f __CFRunLoopRun + 1263
29 CoreFoundation 0x00000001050fce11 CFRunLoopRunSpecific + 625
30 GraphicsServices 0x000000010a6731dd GSEventRunModal + 62
31 UIKitCore 0x000000010d23281d UIApplicationMain + 140
32 Todoey2 0x0000000101aef817 main + 71
33 libdyld.dylib 0x0000000104ce9575 start + 1
)
libc++abi.dylib: terminating with uncaught exception of type NSException

Answer 1

This is an index out-of-bounds exception:
'RLMException', reason: 'Index 2 is out of bounds (must be less than
2).'
This happens when you subscript an array with an index that is greater or equal to the length of the array (equal to, because array indexes start at 0 not 1).
if let categoryForDeletion = self.categories?[indexPath.row]
The above line will crash if row >= self.categories.count. I would suggest looking into the numberOfRowsForSection function to figure out why you have more rows than categories.

Answer 2

Hard to tell whats going on with very little code.
I'd suggest littering your code with print statements (especially for your array counts, indexpath.row in cellForRow, editActionsForRowAt etc) and see where it's going wrong.
Looks like you are calling delete on a row that doesn't exist in your realm database, because of which it is crashing.
Here's how I'd update the closure
{ action, indexPath in
// handle action by updating model with deletion
print("\(indexPath.row)")
print("\(self.categories?.count)") //if these two mismatch, that's the problem
if let categoryForDeletion = self.categories?[indexPath.row] {
do {
try self.realm.write {
self.realm.delete(categoryForDeletion)
}
} catch {
print("Error deleting the category, \(error)")
}
}
}