iPhone Core Data Migration With Multiple Models

Question

I have two models at my project, I want to allow versions to one of them. Here's what I did:

• Selected the modelOne.xcdatamodel then Design > Data Model > Add Model Version.
• Clicked command + i then add version to modelOne.xcdatamodel inside modelOne.xcdatamodeld
• Modified modelOne.xcdatamodel, just added some attribute.

• At the delegate I added the options dictionary to the NSPersistentStoreCoordinator, and I get the NSManagedObjectModel by merging the two models like:

   NSString *path1 = [[NSBundle mainBundle] pathForResource:@"modelOne" ofType:@"momd"]; NSURL *momURL1 = [NSURL fileURLWithPath:path1]; NSManagedObjectModel *modelOne = [[NSManagedObjectModel alloc] initWithContentsOfURL:momURL1]; NSString *path2 = [[NSBundle mainBundle] pathForResource:@"modelTwo" ofType:@"mom"]; NSURL *momURL2 = [NSURL fileURLWithPath:path2]; NSManagedObjectModel *modelTwo = [[NSManagedObjectModel alloc] initWithContentsOfURL:momURL2]; NSManagedObjectModel *managedObjectModel = [NSManagedObjectModel modelByMergingModels:[NSArray arrayWithObjects:modelOne, modelTwo, nil]]; 

• Last I did a clean and build, I got error about 'Can't find model for source store'.

Any idea how I could fix this? (Note: if I just use mergedModelFromBundles, I got another error about 'Can't merge models with two different entities named Entity1'

Answer 1

I had a similar problem. It turned out that the old .mom complied model file was still in the app bundle on the simulator. Apparently, when you clean a project it doesn't wipe the app bundle on the simulator. Manually deleting the app off the simulator and then cleaning before building again solved the problem.