Thank you Greg. Now i know it can be done. much appreciated! Sandro.
On 2010-06-07, at 11:46 AM, Greg Reichow wrote: > >> Greetings. >> >> I'm building a iPhone application which is database driven. >> in that application i've designed it to have two databases. >> One database will be distributed with the application and is meant to be >> read only. >> the second database is meant to copy items to it for the user's safe keeping. >> >> the reason for this is that the application update will also include a >> refreshed database >> and as such if i only link to the records it might happen that the record >> that the user >> wished to keep would of been purged from the original database. >> >> evidently the structure is quite the same on both, with the exception of >> some additional fields >> in the user database. >> >> when the application starts it complains that it can not merge the two >> models. >> i've been looking on the net but found nothing of significance. >> >> is it possible to have two separate database in the same application on the >> iphone. >> and what are the steps to make it happen. >> >> do i have to duplicate the Core data initialization procedures and maintain >> 2 distinct managed object contexts? > > I have a very similar application requirement. In my case, I am using 2 > separate persistent stores. One is the user store located in their > documents directory to maintain their unique copy of the database and edits > to the provided data. The second is part of the application bundle. In this > case, I use 2 separate MOC's and migrate data from the app persistent store > to the user persistent store. Using the metadata that can be stored with the > persistent stores, I check a version key I create and then if it is > different, do a merge of the 2 stores. See the core data docs for a method > for efficiently doing a large comparison and merge. This has worked quite > well and allows for application database updates without messing up any > unique changes the user has made to their own earlier copy. > > Doing it this way also protects the user if the application is reloaded. The > user data in the documents directory is backed up and can easily be restored. > > As for model changes, if they are simple changes to the model between > versions, you may be able to get away with lightweight migration. It is a > simple option to add when loading the persistent store. > > There very well may be a better approach but this has successfully worked for > me. > > Greg Reichow > MangoCode _______________________________________________ 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
