Core Data - how to handle _persistentStoreCoordina

Question

I'm just putting the finishing touches to my app for its first release. I've successfully implemented Core Data but not sure what to do about the persistentStoreCoordinator method that says "Replace this implementation with code to handle the error appropriately."

If I change the model for an update I will look into migration but for now what should I do here?

// Returns the persistent store coordinator for the application.
// If the coordinator doesn't already exist, it is created and the application's store added to it.
- (NSPersistentStoreCoordinator *)persistentStoreCoordinator
{
    if (_persistentStoreCoordinator != nil) {
        return _persistentStoreCoordinator;
    }

    NSURL *storeURL = [[self applicationDocumentsDirectory] URLByAppendingPathComponent:@"Data.sqlite"];

    NSError *error = nil;
    _persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:[self managedObjectModel]];
    if (![_persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeURL options:nil error:&error]) {
        /*

         Replace this implementation with code to handle the error appropriately.

         abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.

         Typical reasons for an error here include:
         * The persistent store is not accessible;
         * The schema for the persistent store is incompatible with current managed object model.
         Check the error message to determine what the actual problem was.


         If the persistent store is not accessible, there is typically something wrong with the file path. Often, a file URL is pointing into the application's resources directory instead of a writeable directory.

         If you encounter schema incompatibility errors during development, you can reduce their frequency by:
         * Simply deleting the existing store:
         [[NSFileManager defaultManager] removeItemAtURL:storeURL error:nil]

         * Performing automatic lightweight migration by passing the following dictionary as the options parameter:
         @{NSMigratePersistentStoresAutomaticallyOption:@YES, NSInferMappingModelAutomaticallyOption:@YES}

         Lightweight migration will only work for a limited set of schema changes; consult "Core Data Model Versioning and Data Migration Programming Guide" for details.

         */
        NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
        abort();
    }

    return _persistentStoreCoordinator;
}

Answer 1

The failure of a NSPersistentStore being added to a NSPersistentStoreCoordinator is a developer level error. This should never fail in production if you have done adequate testing. Therefore I always put my own version of the following:

NSLog(@"Failed to load persistent store: %@\n%@", [error localizedDescription], [error userInfo]);
abort(); //My personal version throws a NSException

This is a hard error and should be a hard error 99% of the time. This absolutely should crash in development so that you can know if it happens and you are forced to solve it. Since it is a developer level error you can leave this code in place since it should never happen in production and if it does, you want a crash report sent to Apple.