Core Data crash when saving with error : _Unwind_Resume called from function -[NSSQLCore performChanges] in image CoreData

I am a bit stuck on this core data error. My basic setup on the app is to load some basic data at initialization. Lets call them Department and Employees. At initialization, I would only load the departments and employees related to the current user of the app.

Then the user has the ability to search for other department and/or employees. When they do a search, for example, for the Arts department, the server returns the first 20 employees from t开发者_运维技巧hat department. The code stores the new department into core data, and also stores the employees into core data. I am using 2 threads, one to the actual work of storing the data into the context, and the other to show the data on the GUI. I use the mergeChangesFromContextDidSaveNotification method to merge the changes.

The storing of the department always works, but the line :

BOOL ok = [importContext save:&errorSave];

always causes the _unwind_resume error. I've taken the advice from here. Turned on stop on Objective C exceptions. And I see this call stack.

#0  0x030203f4 in objc_exception_throw ()
#1  0x0253d921 in -[NSSQLiteConnection updateRow:] ()
#2  0x0253c6b4 in -[NSSQLConnection performAdapterOperations:] ()
#3  0x0253c35e in -[NSSQLCore _performChangesWithAdapterOps:] ()
#4  0x0253ae3a in -[NSSQLCore performChanges] ()
#5  0x02534778 in -[NSSQLCore saveChanges:] ()
#6  0x024f27c9 in -[NSSQLCore executeRequest:withContext:error:] ()
#7  0x025a134b in -[NSPersistentStoreCoordinator executeRequest:withContext:error:] ()
#8  0x0252b088 in -[NSManagedObjectContext save:] ()

Which doesn't give me any clue on why the save is causing this exception.

I had a look at the data I am trying to save by printing it out just before the save and it looks ok. There are usually 1 or 2 employees that have already been imported, and they are updated (as required), and the other employees are inserted. The import context seems to see that correctly.

I also checked to make sure that the datamodel doesn't have invalid non-optional attributes.

I thought the problem might be due to threading, so I've moved everything to the same thread, just to check. Nope, problem still there.

So now, I am a bit stuck on what to try next? Any suggestions would be greatly appreciated.

I'm pretty sure _Unwind_Resume is part of the exception handling stack. So, really all it tells you is that an exception occurred that the system couldn't handle.

I would comment any retains and releases you might have on managedObjects, especially any you may have marked as autorelease. Mismanaging release can cause an unsaved managedObject to disappear from the object graph creating a w

Ok, strange as it seems, I think the issue was a mis-match of types in the datamodel and the actual data. in the data model, I defined one of the fields incorrectly as Int32, where in actual fact it should have been a float.

Although I don't fully understand why on the first save it always works, but the second time i try to save, I get the above error.

With the data type change, now, multiple saves works as expected.

Wish the error message was a little less opaque!