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copied!<p>You should probably get a copy of Marcus Zarra's Core Data book and read up on migration (Ch. 5). But, failing that, there are some basics that are good to know. First, you need both your old model (schema) and your new model in your updated app. Second, you need to make sure that the new model is tagged as being the "current model". Third, you need to make sure that you create your NSPersistentStoreCoordinator in such a way that it automatically maps from existing model (as loaded from disk) to new model.</p> <pre><code>- (NSPersistentStoreCoordinator *)persistentStoreCoordinator { if (persistentStoreCoordinator) return persistentStoreCoordinator; NSURL *storeUrl = [NSURL fileURLWithPath: [[self applicationDocumentsDirectory] stringByAppendingPathComponent: @"MyDataStore.sqlite"]]; NSError *error = nil; persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel: [self managedObjectModel]]; // Use mapping model NSDictionary *options = [NSDictionary dictionaryWithObjectsAndKeys: [NSNumber numberWithBool:YES], NSMigratePersistentStoresAutomaticallyOption, nil]; if (![persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeUrl options:options error:&error]) { [NSApp presentError:error]; } return persistentStoreCoordinator; } </code></pre> <p><strong>Update</strong> Your old model in your new app needs to be <strong>exactly</strong> the same as the model in your old app. If you are unsure that this is the case, then there are some steps that you can take to make sure. The way I do it is a bit involved - but I will outline it if/when you think that that would be helpful.</p>

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