Error after deleting NSManagedObject "The operation couldn’t be completed" - iphone

Question

so I'm having a Core Data & iCloud combined Database that is working fine for me.
Some users though had a certain crash after trying to delete NSManagedObject's that are respresented in an UITableView. In the debug-logs that I attach to the crashreports there is the following error-log before the crash:
2013-05-08 22:38:51.851 MyApp[11819:907] Unresolved error Error Domain=NSCocoaErrorDomain Code=134030 "The operation couldn’t be completed. (Cocoa error 134030.)", {
}
Unfortunately the info about the error: {} is empty and I never had the error myself, so I don't know how to recreate it. It did occur at least 21 times for customers though.
(Whats even worse is, once they reopen the App, some NSManagedObject is in an invalid state and my tableview has problems loading it. But that just at the side)
The actual error is "SIGABRT" in " tableView:commitEditingStyle:forRowAtIndexPath:", here is the respective code:
- (void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath {
if (editingStyle == UITableViewCellEditingStyleDelete) {
ICLog(#"Deleting the row %i,%i from the data source", indexPath.row, indexPath.section);
NSManagedObjectContext *context = [self.fetchedResultsController managedObjectContext];
[context deleteObject:[self.fetchedResultsController objectAtIndexPath:indexPath]];
//Save the context
NSError *error;
if (![context save:&error]) {
NSLog(#"Unresolved error %#, %#", error, [error userInfo]);
}
}
}
PS: From the Logs its also clear that this is all run from the main thread.
Anyone here who had this problem too?
UPDATE:
Luckily I had the same error in another App I'm working on just now, in a device I have access too (so far I had never saw this happening on any of my devices), so now I can investigate it while it happens. This is what I found out:
a) it still occurs after switching off icloud in the settings
b) the error occurs everytime I try to delete or insert any NSManagedObject, even if I do it in my Appdelegate right after starting, without ever accessing the data somewhere else
So it seems like something completely stops my databse from being updated. I can catch the above the exception, then the App at least isn't crashing. But of course no changes to the database are saved.

Answer 1

Errors on [context save:] often occur when you try to save an invalid state of your datamodel.
Since you have deleted an object before, i would suspect that this object was in a relation with some other object that still is present, but now has it's relation in an invalid state (nil for a relation that is non-optional)
Checking your delete rules could help, maybe some relation to the object you delete needs to be optional or you have to propagate the deletion correctly.

Answer 2

I will be making some assumptions here.
What I can see is that you delete the CoreData object using the object in fetchedResultsController but you never unset the object from whatever you use as your ViewController iVar fetch storage in numberOfRowsInSection and re-organise your table index after deletion.
Let say your original [indexPath.row count] is 7 then you go on and delete indexPath.row = 5 from your tableView. Then you go on and try to delete another object at indexPath.row = 6 that item exists on your tableView index because you havent re-organised the indexs, but it wont exist in CoreData.... given that now the max count is 6 that the index value is now 5 of what originally was 6.... This could be what your users are experiencing...
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
return [yourFetchedDataVariable count];
}
- (void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath {
if (editingStyle == UITableViewCellEditingStyleDelete) {
ICLog(#"Deleting the row %i,%i from the data source", indexPath.row, indexPath.section);
NSManagedObjectContext *context = [self.fetchedResultsController managedObjectContext];
[context deleteObject:[self.fetchedResultsController objectAtIndexPath:indexPath]];
//Save the context
NSError *error;
if (![context save:&error]) {
NSLog(#"Unresolved error %#, %#", error, [error userInfo]);
}
// the possible solution
[yourFetchedDataVariable removeObjectAtIndex:indexPath.row];
// also now you want to re-order your array index...
[yourTable reloadData]; // and re order your table indexses aswell
}
}

Answer 3

The optional relationship are you sure it is optional? and optional in what sense to Xcode? I ahd this issue once and it was due to a "optional" relationship.