Thanks for the response, >> With SmartGroups the situation is different. The relationship is not >> explicit; it is due to the fact that the entity's name is used in the >> predicate. If the user deletes the referenced entity the predicate will no >> longer be valid. This is possibly okay in that the predicate will return no >> group members. But if the entity is has its key field (name in this case) >> changed then the predicate will be incorrect; this is clearly not what the >> user expects to happen. Furthermore, the most serious problem is that it >> breaks NSPredicateEditor since there is no longer a popup menu item matching >> the deleted project. NSPredicateEditor cannot display this predicate so that >> the user can edit it to fix the problem. >> >> I think it would be reasonable to let the user know that the proposed >> deletion will invalidate one or more existing SmartGroups and give him/her >> the option on how to deal with the situation. For a name change I could just >> silently update the predicate as long as I can arrange for a timely >> notification. >> >> One possible solution is parse the SmartGroups's predicate each time it is >> set and then create an explicit bi-directional relationship between the >> SmartGroup object and the referenced entity. Then using KVO, I could >> determine all the SmartGroups that are referencing the to-be deleted entity. >> But I would need to do this before the entity is deleted, not wait until the >> save is attempted by Core Data. >> >> So, before implementing the above solution, I thought I would post to the >> list to see if anyone has any suggestions for me. Am I modelling the >> situation correctly? Is it possible to accomplish what I want (essentially >> intercept entity deletion) in a reasonably elegant manner? > > Even if you could capture a proposed deletion before save, which AFAIK you > can't, you will still have an undo mess. IMHO you best bet is to capture the > situation at the point of editing the predicate, substituting the deleted > item with a placeholder like "<deleted>". I agree, trying to capture the deletion would be an unholy mess.
But perhaps I haven't explained the problem clearly enough. The problem arises not when the predicate is being edited, but when entity referenced in the predicate is deleted. I need to find a way to notice this and then to take corrective action. Also, it would be nice to let the user know that the deletion of this entity will invalidate a SmartGroup. Once the model is changed appropriately I can perform this check in response to the user request to delete the entity. > > HTH, > > 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
