On Sep 18, 2010, at 5:41 AM, Amy Gibbs wrote: > Hi, > > in a core data app, is there an easy way to 'merge' two instances of an > entity, for example where something has been accidentally added twice, and > each instance has it's own relationships.
There is no "automatic" or "built-in" way, but Core Data makes changing relationships easy, so it will likely be easy. > I'd like to merge the two instances into a single one where basically all of > the second instances relationships are copied to the first instance, then the > second instance is deleted. In my scenario I think it would be OK to just > 'add' the second instances details to the first, I don't see that anything in > the second instance would cause data/relationships to be deleted in the first. > > If I have to do this manually, is it that simple, just copy the relationships > (not that I know how to do that but it must be possible) and delete the > second instance? How you handle migrating to-many relationships depends on the merge logic you need to use. Whether to-one or to-many, if you are replacing object A's relationships with object B's, you can use the direct setter method. Otherwise for to-many, you can add one at a time using -mutableSetValueForKey:, deciding on an object by object basis whether to add or not. Of course, all of this assumes a one-way update (versus a sync, which requires knowing additional state info). Keary Suska Esoteritech, Inc. "Demystifying technology for your home or business" _______________________________________________ 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
