I keep on getting "save operation failure" after any change on my XCode Data Model

Question

I started using Core Data for iPhone development. I started out by creating a very simple entity (called Evaluation) with just one string property (called evaluationTopic). I had following code for inserting a fresh string:

• (void)insertNewObject {

  // Create a new instance of the entity managed by the fetched results controller. NSManagedObjectContext *context = [fetchedResultsController managedObjectContext]; NSEntityDescription *entity = [[fetchedResultsController fetchRequest] entity]; NSManagedObject *newManagedObject = [NSEntityDescription insertNewObjectForEntityForName:[entity name] inManagedObjectContext:context];

  // If appropriate, configure the new managed object. [newManagedObject setValue:@"My Repeating String" forKey:@"evaluationTopic"];

  // Save the context. NSError *error; if (![context save:&error]) { // Handle the error... }

  [self.tableView reloadData];

}

This worked perfectly fine and by pushing the +button a new "My Repeating String" would be added to the table view and be in persistent store.

I then pressed "Design -> Add Model Version" in XCode. I added three entities to the existing entity and also added new properties to the existing "Evaluation" entity. Then, I created new files off the entities by pressing "File -> New File -> Managed Object Classes" and created a new .h and .m file for my four entities, including the "Evaluation" entity with Evaluation.h and Evaluation.m. Now I changed the model version by setting "Design -> Data Model -> Set Current Version". After having done all this, I changed my insertMethod:

• (void)insertNewObject {

  // Create a new instance of the entity managed by the fetched results controller. NSManagedObjectContext *context = [fetchedResultsController managedObjectContext]; NSEntityDescription *entity = [[fetchedResultsController fetchRequest] entity]; Evaluation *evaluation = (Evaluation *) [NSEntityDescription insertNewObjectForEntityForName:[entity name] inManagedObjectContext:context];

  // If appropriate, configure the new managed object. [evaluation setValue:@"My even new string" forKey:@"evaluationSpeechTopic"];

  // Save the context. NSError *error; if (![context save:&error]) { // Handle the error... }

  [self.tableView reloadData];

}

THIS DOES NOT WORK THOUGH!!!!! Every time I want to add a row the simulator crashes and I get following:

"NSInternalInconsistencyException', reason: 'This NSPersistentStoreCoordinator has no persistent stores. It cannot perform a save operation.'"

I had this error before I knew about creating new version after changing anything on the datamodel, but why is this still coming up? Do I need to do any mapping (even though I just added entities and properties that did not exist before?). In the Apple Dev tutorial it sounds very easy but I have been struggling with this for long time, never worked after changing model version. Anyone?

Answer 1

Do you have NSMigratePersistentStoresAutomaticallyOption and NSInferMappingModelAutomaticallyOption options set when you create your persistentStoreCoordinator in the App Delegate?

- (NSPersistentStoreCoordinator *)persistentStoreCoordinator {

    if (persistentStoreCoordinator != nil) {
        return persistentStoreCoordinator;
    }

    NSURL *storeUrl = [NSURL fileURLWithPath: [[self applicationDocumentsDirectory] stringByAppendingPathComponent: @"database.sqlite"]];

    NSError *error = nil;
    NSDictionary *options = [NSDictionary dictionaryWithObjectsAndKeys:
           [NSNumber numberWithBool:YES], NSMigratePersistentStoresAutomaticallyOption,
           [NSNumber numberWithBool:YES], NSInferMappingModelAutomaticallyOption, nil];
    persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel: [self managedObjectModel]];
    if (![persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeUrl options:options error:&error]) {
        // Handle error
    }    

    return persistentStoreCoordinator;
}

Answer 2

If you are only getting this error in the Simulator then you have changed your data model and it hasn't deleted the sqlite file that you were previously using.

So go to: ~/Library/Application Support/iPhone Simulator/User/Applications/

Then look through the HEX-named folders until you see your app. Open the Documents directory and delete the sqlite file. The error should go away.

Answer 3

if you are running this on the simulator/iphone, also uninstall the app too. worked for me on the simulator only after i deleted the app!