无法获取核心数据永久存储的元数据

Question

I am using RESTKit backed by Core Data. I am trying to detect whether or not I have a new core data model version. I have it set up to map changes automatically I just need to detect the migration to update the UI. My code is:

NSError *error;
NSURL *sourceURL = [NSURL fileURLWithPath:[[NSBundle mainBundle] pathForResource:@"Model" ofType:@"momd"]]
NSDictionary *sourceMetadata = [NSPersistentStoreCoordinator metadataForPersistentStoreOfType:nil URL:sourceURL error:&error];
BOOL needsMigration = ![[self managedObjectModel] isConfiguration:nil compatibleWithStoreMetadata:sourceMetadata];

The sourceMetadata variable is always nil and I can't seem to figure out why. The error message is not very helpful to me:

Error Domain=NSCocoaErrorDomain Code=134000 "The operation couldn't be completed. (Cocoa error 134000.)"

Where am I going wrong?

Answer 1

Your error is that sourceURL is the path of your model file:

NSURL *sourceURL = [NSURL fileURLWithPath:[[NSBundle mainBundle] pathForResource:@"Model" ofType:@"momd"]]

That is, Model.momd , in the app bundle. You need to use the path to your persistent store file, probably $SOMETHING.sqlite and probably in your app's documents directory.

Error 134000 is NSPersistentStoreInvalidTypeError , which Apple describes as "Error code to denote an unknown persistent store type/format/version". That suggests that either something's wrong with the persistent store file at your URL or that maybe it's missing. The first thing to do is look at error and see what NSPersistentStoreCoordinator is trying to tell you. There's a good chance that it's telling you exactly what's wrong, but that you're not listening.

If a file exists at that URL, it might help to change the first argument to the lookup call from nil to NSSQLiteStoreType , or whatever store type you're using.