Cannot remove an observer ... for the key path "..." from ... because it is not registered as an observer

I have a Core Data model with two entities: A and B. A has a relation to one or more Bs. B has a property bValue.

I create many instances of a class and some of them invoke a notification. This notification called a method that creates a new B entity and adds it to A. The instances are created using NSThread in order to make the UI more responsive.

This works only fine then there are no开发者_运维知识库t too many notifications invoked. Or at least not too many at 'the same time'.

Then I get this exception:

Cannot remove an observer <NSArrayController 0x10016c150> for the key path "bValue" from <bValue 0x104e55c30> because it is not registered as an observer.

Yes, B is bound to an NSArrayController.

• If I remove this ArrayController from the NIB file, everything works fine (except everything the ArrayController has to do)
• If I create many Bs and add them to A elsewhere (outside the notification method) everything works find, also with the ArrayController.

Can someone help me please?

(Please excuse my poor pronunciation.)

You said you're doing this work on a separate thread. If so, you need to make sure you are using a separate NSManagedObjectContext. You cannot use the same NSManagedObjectContext on multiple threads, nor can you use a NSManagedObject associated with one MOC in another MOC. Each thread needs to interact with CoreData independently.