iOS crash 'NSInternalInconsistencyException', reason: 'statement is still active' Core Data cache related?

Question

Very occasionally seeing these pop up in crash reports on screens using NSFetchedResultsController, and not sure how to address them. I don\'t believe I\'m using th

Answer 1

It's more than likely that this is a threading problem in some way or another. There isn't quite enough information in the question to see for sure, but it's worth check through the crash logs and looking at the stack traces for all threads at the time of the exception, and see if any other threads are doing anything which interacts with a managed object. It could be that you have a notification handler, a URL connection completion handler, or some other bit of code using concurrency which you hadn't noticed, using core data objects in the background. It's worth noting that setting or accessing any property on any managed object from a context that's being used on more than one thread could potentially trigger this kind of exception, which can make it pretty tough to diagnose.

The relatively simple solution to solving these problems in most apps is to push the execution of that code to the main thread (using dispatch_async()). Alternatively, if you've got lots of processing to do it might be better to create a child context on the background thread and re-fetch the object from the child context, then save the child context. Of course, to re-fetch the object you need to have its objectID, which is a property which can only be accessed on the thread the object was originally fetched on…

Answer 2

Got this error while simultaneously requesting data with NSFetchedResultController (from main thread context) and NSFetchRequest through my background context.

The way I have handled this is by making each of my MOCs have its own persistent store coordinator. Both of the persistent store coordinators talk to the same persistent store on disk.