Core Data fetch request fails with: 'NSInternalInconsistencyException', reason: 'statement is still active'

Question

Basic app layout using the navigation controller template with core date:

Delegate: persistenceCoordinator, managedObjectModel, managedObjectContext

• RootView: managedObjectContext (from delegate), addManagedObjectContext (using the pattern from the templates), fetchResultsController
  • Add/Edit view (a hierarchy for adding Object A & its B)

I have two objects, A & B that share a 1-to-1 relationship/inverse relationship

Using the pattern from the templates the app:

1. Creates an addManagedObjectContext
2. Inserts an A entity
3. Pushes on the Add/Edit A view (having passed it the inserted entity)

EXCEPTION STEPS 1:

If I simply fill in the A attributes and save everything works fine.

• The object is inserted into the database (verified with sqlite3 on the command line)
• The fetchResultsController updates the list view
• I can close and open the app (full close/open not just app switch) and the list view will re fetch correctly

If I then Edit A, I can select Add B and an add B view is pushed on (and passed the A entity)

• Fill in B details and save
• B is inserted into A's managedObjectContext, the relationship is set, and the context is saved
• The view pops off and all appears well
• The objects are both in the database with the correct relationship
• I can reload the record and see the relationship, make edits etc
• EXCEPTION: If I close/reopen the app, so as to trigger a fetch, then the error mentioned in the title will occur.

EXCEPTION STEPS 2:

If I fill in the A attributes AND the B attributes in the initial "add"

• Saving B triggers a full save of A's context (as above)
• Saving A saves via the delegate relationship set up by the template (and merges the result into the main managedObjectContext etc)
• The objects are inserted into the database correctly
• However the fetchResultsController DOES NOT update to show the new records
• EXCEPTION: If I close/reopen the app, so as to trigger a fetch, then the error mentioned in the title will occur.

I've tried saving A first, adding a separate context for B etc etc. I'm confused to say the least. Any help would be greatly appreciated.

Cheers, Ryan

Answer 1

It sounds like you have two or more managed object context when you just need one.

I don't know why you would have a method called addManagedObjectContext in the RootViewController or what it would do. In all but the most complex designs, you have only one context at a time and they don't overlap. The context/s should be held by the app delegate or a dedicated model object. You would never create a new context every time you open a particular view.

You can have different context all writing to the same persistent store so I think this is why you are seeing the data in the store. However, you can't maintain graph integrity across context if you put one object in a relationship in one context and the other side of the relationship in another context. I believe this is what is producing your error.

Answer 2

This error is generally related to threading and probably means something is still processing on another thread. In my case I was doing something stupid in a managed object's init (don't override init ;)).