Core Data, KVO, and NSInternalInconsistencyException

Question

I'm using Core Data and KVO to look for changes in values to trigger saves to the data store. I have a table view with search hooked up to NSFetchedResultsController. When the search changes, a new results controller is made on pressing the Search button. When the user selects an item in the results table view, then the user enters a detail view and can make edits.

This is where I encounter the problems. When the user makes a change in a separate UIControl that I made, the detail view is notified and can use the NSFetchedResultsController it remembers from when the table view pushed me onto the view stack to get the NSManagedObjectContext and do a save. When I do so, I sometimes get the following error:

Serious application error.  Exception was caught during Core Data change processing.  This is usually a bug within an observer of NSManagedObjectContextObjectsDidChangeNotification.  no object at index 89 in section at index 0 with userInfo (null)
Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'no object at index 89 in section at index 0'

I found that this tends to happen when I do a search and an object that isn't on the top of the table is moved up to the top. I vaguely know what might be wrong in the back of my head, but would appreciate any pointers as to how to fix this.

Answer 1

I figured out what was wrong. I forgot to unset the old NSFetchedResultsController's delegate, and also forgot to release said NSFetchedResultsController. My UITableView subclass also responded to updates to the NSFetchedResultsController through delegates, and caused weird calls to be made.