Core Data Migration error message "'Model does not contain configuration 'XYZ'.'"

I have a Managed Object Context to which I add two different SQLite stores. I use Configurations in the Mananged Object Model to assign certain entities to one store and other entities to the other. The Configurations are called "UserDB" and "MainDB".

Everything works okay until I try to use automatic migration. After creating a new Managed Object Model version, and adding a new attribute to one of the entities in the UserDB Configuration, I get an exception when adding the old version store (for the User开发者_如何学编程DB related store) to the store coordinator: 'Model does not contain configuration 'UserDB'.' I can find no hits for this error on Google. Anyone out there using multiple stores with Configurations? Anyone have an idea what I might be doing wrong?

The stack looks like this:

objc_exception_throw
-[NSManagedObjectModel isConfiguration:compatibleWithStoreMetadata:]
-[NSStoreMigrationPolicy sourceModelForStoreAtURL:metadata:error:]
-[NSStoreMigrationPolicy(InternalMethods) _gatherDataAndPerformMigration:]
-[NSPersistentStoreCoordinator addPersistentStoreWithType:configuration:URL:options:error:]
-[MyAppDelegate persistentStoreCoordinator] 

---

This looks like a bug with migration+configurations. I was able to work around the problem by going through the same motions and passing nil for configuration when calling addPersistentStoreWithType. The migration happens, and then I can make a new persistent store coordinator and add the stores again with the proper Configuration string arguments.

This is the second configuration related bug I've run into. Not a well tested feature apparently.

---

I had the same problem. The fact pattern was identical and the error message the same. It turned out, however, to be the result of my own mistake.

Let's say the old model was Blah.xcdatamodel and the new Blah 2.xcdatamodel. I had started making changes to Blah before realising my mistake and creating Blah 2. I then used my version control system (Git) to revert to the old Blah and then recreated Blah 2. Everything looked right. But I must have done something wrong in the reversion process, because when I thought to double check that Blah.xcdatamodel in my current project folder was really the same as Blah.xcdatamodel in the project folder I used to build the previous version of the app (fortunately I always keep a zipped archive of the project folder for each released version as I don't fully trust version control systems), I found that they were in fact different, albeit that they looked identical in XCode. The file size was different, for instance.

I substituted the old Blah into my current project folder, and lo and behold it all went perfectly, without any need for the workaround described by Ken.

I am not saying that Ken had necessarily made a similar mistake, but if you do encounter this message it is at least worth confirming that the model you are migrating from is REALLY the model that was used to create the data in question.