Join/union two NSManagedObjectContexts

Question

I have one main NSManagedObjectContext with some entities and another background NSManagedObjectContext with same objects as the main NSManagedObjectContext. I add some objects to the background NSManagedObjectContext (that may exist in the main NSManagedObjectContext) and basically what I want is to be able to join the two NSManagedObjectContext instances thus making CRUD (create,read update and delete) on the objects from both NSManagedObjectContext instances so they're mirrored 1:1.

Is this possible?

Answer 1

NSManagedObjectContext instances are just scratch pads. They both point to the same underlying NSPersistentStoreCoordinator. Therefore when you call -save: in one NSManagedObjectContext then the NSPersistentStoreCoordinator will get updated and you can retrieve those changes into the other NSManagedObjectContext.

If your "background" NSManagedObjectContext is a child of your "main" NSManagedObjectContext then just calling -save: on the background NSManagedObjectContext will cause the main NSManagedObjectContext to be updated automatically. That is one of the benefits of the parent/child design.

In any case, the NSManagedObjectContext instances are just temporary until you save. When you save, those changes all go to the same place; the NSPersistentStoreCoordinator.