Question

I am receiving a “CoreData could not fulfill a fault for …” error message when trying to access a new attribute in a new data model. If I work with new data I’m ok, but when I attempt to read existing data I get the error. Do I need to handle the entity differently myself if the attribute isn’t in my original data? I was under the impression that Core Data could handle this for me. My new attribute is marked as optional with a default value.

I have created a new .xcdatamodel (and set it to be the current version) and updated my NSPersistentStoreCoordinator initialization to take advantage of the lightweight migration as follows:

NSDictionary *options = [NSDictionary dictionaryWithObjectsAndKeys:      
         [NSNumber numberWithBool:YES], NSMigratePersistentStoresAutomaticallyOption,
         [NSNumber numberWithBool:YES], NSInferMappingModelAutomaticallyOption, nil];

NSError *error = nil;
persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] 
          initWithManagedObjectModel:[self managedObjectModel]];

if (![persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType 
            configuration:nil URL:storeUrl options:options error:&error]) 
{
    NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
    abort();
 }    

Any help is appreciated.

UPDATE:
After more digging I’ve updated my managedObjectModel to:

- (NSManagedObjectModel *)managedObjectModel {

    if (managedObjectModel != nil) {
        return managedObjectModel;
    }
    //managedObjectModel = [[NSManagedObjectModel mergedModelFromBundles:nil] retain];    

    NSString *path = [[NSBundle mainBundle] pathForResource:@"< MyModel >" ofType:@"momd"];
    NSURL *momURL = [NSURL fileURLWithPath:path];
    managedObjectModel = [[NSManagedObjectModel alloc] initWithContentsOfURL:momURL];

    return managedObjectModel;
}

This still hasn’t resolved my problems. I’ve clean and rebuilt, but still no love.

Answer 1

Turns out that there was no problem with the versioning. I had some rather (too) complex logic which removed my object from the model and then I later tried to access it.

+1 to Marcus for the additional debugging pointers, they will no doubt come in handy at some point.