NSMergeConflict on iOS7

Question

I have updated my app to support iOS 7 and have been faced with the problem that on one of screens in my [context save]; I get the following error:

Answer 1

I didn't want to mask a potential problem by setting a merge policy without understanding what was causing the NSMergeConflict first.

In my situation I had performed a NSBatchDeleteRequest earlier on in my code. The NSBatchDeleteRequest is performed directly on the persistent store coordinator so the ManagedObjectContext was unaware of the deletions and still held references to deleted objects. When I later referenced one of these objects and tried to save the context, the NSMergeConflict was thrown.

Calling reset() on my moc after performing the deletion fixed the issue.

let fetchRequest = NSFetchRequest(entityName: "Tasks")
let batchDeleteRequest = NSBatchDeleteRequest(fetchRequest: fetchRequest)
try managedContext.execute(batchDeleteRequest)
managedContext.reset()