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 the 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.
