CODEWITHSUNDEEP
iphonecore-datansfetchedresultscontroller
siasl
siasl

Reputation: 487

NSFetchedResultsController Crash

Following steps result in a crash in NSFetchedResultsController.

  1. I try to add the first element to a NSFetchedResultsController backed TableView.
  2. I create a temporary MO object and display a Modal View pane to add new object.
  3. On the Add Sheet (a Modal View Controller), I press Cancel Button to discard the new element.
  4. In the CancelAction callback for Cancel button, I delete the new temporary object I created.
  5. The code till here is exactly similar to Apple sample code for Core Data. The only extra code I have is a call to [tableView reloadData] after the Add sheet is dismissed.
  6. The crash results only if I try to add the first element, since it is related to wrong section count in NSFetchedResultsController.

This results in a crash given below. If I remove redundant call to reloadData, the crash is not visible. If I add a reloadData call to Recipe sample code data, the crash happens there as well.

Is it a known problem with NSFetchedResultsController?

2009-09-13 18:22:45.600 Recipes[14926:20b] * Terminating app due to uncaught exception 'NSRangeException', reason: '* -[NSCFArray objectAtIndex:]: index (0) beyond bounds (0)'

Upvotes: 1

Views: 1851

Answers (1)

Massimo Cafaro
Massimo Cafaro

Reputation: 25419

As you discovered by yourself, you should NOT use [tableView reloadData], because you are probably using the NSFetchedResultsController delegate methods

– controllerWillChangeContent:
– controller:didChangeObject:atIndexPath:forChangeType:newIndexPath:
– controller:didChangeSection:atIndex:forChangeType:
– controllerDidChangeContent:

These methods are actually in charge of updating your table view when you add, delete or modify objects. Therefore, when you add the call to [tableView reloadData] what happens is that two different threads are both accessing/modifying your table view. This causes the crash you are experiencing.

If you are not using the delegate methods, then the crash is due to something else in your code.

Upvotes: 4

Related Questions