On Jan 16, 2009, at 02:51, Samuel Strupp wrote:
does anybody know, how to migrate an object model with abstract entities correctly? The compiler throws errors for the mapping model "can't auto generate value expression with nil mapping name". I found no documentation about migration with abstract entities in core data under Mac OS X 10.5!
I believe it's been stated on this list that this is not supported, at least not automatically.
However, I did get it working, though I don't remember the details exactly. IIRC, if you examine the auto-generated mapping model you'll see that the concrete entities are missing the property mappings for their properties inherited from abstract entities. If you just want to preserve those properties, you can just create your own property mappings for the concrete properties. The abstract entities might contain the mappings you want to copy (there but not used), or just look at a similar mapping elsewhere in the model, and use it as a template.
Also IIRC, you don't need both directions of a relationship that has an inverse. Setting either direction will change both directions, in the usual Core Data manner.
The bad news is that abstract entities will cause NSPersistentDocument's Save As to break, since it apparently uses a Core Data migration to implement Save As, with an auto-generated mapping model, which of course fails to copy the inherited relationships properly. (My solution was to stop using abstract entities in the next version of the data model. :) )
_______________________________________________ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
