Question

I hava a UINavigationController. The first level is a UITableViewController, the second level just shows details on one of the items of the table view.

In this detail view, I can delete the item. It deletes the underlying managed object.

When I pop back to the view, I have a crash. I understand why, it’s because I didn’t update the cached array that contains the data.

I looked at several tutorials and I don’t exactly understand how am I supposed to handle deletion. Maybe I don’t understand exactly where I should fetch the objects in the model. Should I do a query for every cellForRowAtIndexPath and take the item in the result at position indexPath.row? It doesn’t look efficient. Should I check for changes somewhere and recache the whole query in an array. I would think CoreData would provide something more natural but I couldn’t find it so far.

Thanks in advance.

Answer 1

It is fairly simple. In the child view you should (really, really should) have a reference to the NSManagedObject you are working with. When you want to delete it then you just:

NSManagedObjectContext *moc = [[self myObject] managedObjectContext];
[moc deleteObject:[self myObject]];
NSError *error = nil;
if (![moc save:&error]) {
  NSLog(@"Save failed: %@\n%@", [error localizedDescription], [error userInfo]);
}

This will delete the object. The parent, since it is using a NSFetchedResultsController (which you should also REALLY be doing) will take care of itself.