Core Data error 133020: problems merging in a save:

Question

First off I want to say that I am not using threads or multiple contexts and I have read and worked from every related answer I could find on SO. I have a project which I have a

Answer 1

Have you tried setting the merge policy on your managed object context?

The default is NSErrorMergePolicy which will just throw errors. Your other options are here.

I'd suggest this one :

[self.managedObjectContext setMergePolicy:NSMergeByPropertyObjectTrumpMergePolicy];

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Just noticed something that might be causing problems in your swapping tracks code.

Instead of

OT_Track *track;

track = [[self.tracksArray objectAtIndex: fromIndexPath.row] retain];
[self.tracksArray removeObjectAtIndex: fromIndexPath.row];
[self.tracksArray insertObject:track atIndex: toIndexPath.row];
[track release];

try the code snippet from this blog post.

I think that your track swapping code might be getting indexes confused halfway through the swap.

Answer 2

I'm still not really sure what caused this but the issue reoccurred and I solved it by ensuring that any methods that referenced core data were executed on the main thread using performSelectorOnMainThread.