Question

This is a long shot, since a google search returns absolutely nothing on this. Sometimes, often enough where it merits further investigation but not often enough where I can track down when or how exactly it happens, I get the following exception when I call save: on a NSManagedObjectContext:

-[_NSObjectID_48_0 _stateFlags]: unrecognized selector sent to instance 0x8675570

The context is a child context with type NSPrivateQueueConcurrencyType, which is a child of the main context with type NSMainQueueConcurrencyType.

I really don’t have any further information other than the stack trace:

Can any cryptographers make anything out of the stack trace to conjure up some possible ideas as to what the problem could be?

Answer 1

The log message indicates that for some reason we are looking for the property/method _stateFlags on _NSObjectID_48_0, one of which is a private API, and the other is a private class.

A quick run of

class-dump /System/Library/Frameworks/CoreData.framework/Versions/A/CoreData

seems to indicate that (among other places) _stateFlags is a private API on NSManagedObject. I can’t find any reference to a private class named _NSObjectID_48_0 on my Mac, but based on name alone it seems related to NSManagedObjectID.

This is a long shot, but I am wondering if you have at some point passed an NSManagedObjectID where an NSManagedObject was expected instead? It can’t hurt to grep your code for explicit coercions to NSManagedObject.

Another culprit might be inserting NSManagedObjectIDs into a weakly-typed datastructure (dictionaries/arrays/sets I’m looking at you) which might allow you to “coerce” to NSManagedObject without being explicit about it.