NSFetchedResultsController returns duplicates (the same objectID and reference)

Question

I\'m experiencing a weird behaviour with NSFetchedResultsController. It is new in iOS 10. Straight to the point: fetchedObjects contains duplicate objects.

Answer 1

I've come across similar problem today also. I noticed in my case the fetched objects on the FRC all had temporary IDs. These can be verified like so:

fetchedResultsController.fetchedObjects[0].objectID.isTemporary

To get around this problem in my App I explicitly request permanent object IDs for all the inserted objects before saving the context on which new data is imported/updated/synced:

NSError *error;
[bgContext obtainPermanentIDsForObjects:bgContext.insertedObjects.allObjects error:&error];