Question

I’m new to Core Data and I can’t find the answer into the docs (but I’m sure it’s somewhere):

I defined the properties for my entities and test my third version of an application (ASOC, ObjC, ObjC+CoreData): I write, read, create and remove objects, undo/redo actions, autosave, and everything is working like a charm for the moment (Stefan, my old dictionaries are gone and replaced by… well… managed objects I suppose )

I’m saving my file in binary format. The images, icons, rtfd texts are”Transformed”-type properties, because binding images by data is a deprecated manner which issues a warning (once).

Now: what if I decide to ADD a property to an entity? The previous files become unreadable! The app issues an alert:

The document “xxx” could not be opened. The file isn’t in the correct
format

I suppose Apple has implemented a sort of “backward compatibility”, as the file is archived with keys/properties: when I archived some dictionaries, I could add or remove keys without problems…

Any link welcome!

Answer 1

If i understood you right, you changed your Core Data Model and want to use it with the binary store you used before. If it’s the issue, you need to make a Core Data Migration, the whole process of which is described here.

http://developer.apple.com/library/mac/#documentation/cocoa/conceptual/CoreDataVersioning/Articles/Introduction.html