NSManagedObject's hasChanges is true while changedValues is empty

Question

I am trying to observe individual NSManagedObject changes on NSManagedObjectContextWillSaveNotification:

- (void)managedObjectContextWi         


        

Answer 1

Do you have any transient attributes on your entity? I am seeing the behavior you describe, and I've written some test code that shows that modifying a transient attribute causes hasChanges to return true, while changedValues is empty.

You can avoid this behavior by using setPrimitiveValue:forKey: to modify your transient attribute or the equivalent method generated by Core Data (setPrimitiveFoo: for an attribute named foo). You could also implement the transient attribute's setter to do this for you.