Core data / NSFetchedResultsController error

Answer 1

Here's a tip from Marcus Zarra (author of Core Data book):

http://stackoverflow.com/questions/2017219/core-data-error-when-deleting-row-in-tableview

"Try breaking on objc_exception_throw and see what method is throwing the exception. That should help track it down"

Answer 2

I know it's unlikely to be the answer, but since the crash is occuring on save: and I do remember having an odd error with this once... The error I had was fixed this way, I reckon it's worth a shot.

So, with that said, try changing

NSError *error;

to

NSError *error = nil;

Answer 3

Errors like this on a Core Data save when using the iPhone SDK generally point at an error in the NSFetchedResultsController delegate methods. Specifically one of the example pieces of code from Apple is incorrect and frequently produces this error. I would suggest looking at your delegate methods and compare them with the latest example code as you may find that Apple has updated the example code in the documentation and if you re-copy their code this error can go away.

Hope that helps.