即使已删除该对象，也要使其保持活动状态

Question

I have a controller that presenting objects, some times the during showing this page the some of the objects are deleted. and than , if we try to use this object - all properties are nil.

Is there way to use copy NSMangedobject without connecting him to the real data base as a free object. so when the original object will be deleted , this object will be stable and full of data?

Thanks

Answer 1

It sounds like you want to create a new NSManagedObjectContext for this controller. You need to do it somewhere that you have access to to original context or its persistent store coordinator. You can do this in prepareForSegue:sender: if you load the view controller via a storyboard segue.

The controller needs to load its objects from this context. You can't pass it objects you fetched using the original context. Instead, ask each of those original objects for its objectID and use those ids to create new managed objects using the new context. Create all of the new objects immediately and access a persistent property of each (to un-fault the objects). The new controller must keep a strong reference to each of these objects because the context doesn't necessarily retain them.

As long as you don't send refreshObject:mergeChanges: or mergeChangesFromContextDidSaveNotification: to the controller's private context, all of the objects should remain valid and their properties should not change.

Answer 2

It feels like you use core data objects and some kind of tableview. Use nsfetchedresultscontroller and you will forget about sync problem. btw, it is not safe to keep somewhere managedObjects. possible you can copy and set managedObjectContext property to nil to make it separate from the db but these objects will be not up-to-date then.

Answer 3

If you just want to keep a reference alive for runtime, you would just set a strong reference (eg @property (nonatomic, retain) ). If this isn't enough, you can call [id<NSCopying> copy]