Restore one fetched entity out of many -- Core Data

This question covncerns my lack of understanding of how to use the core data undo manager and how to restore a NSManagedObject to its state before editing was done.

I am just learning my way around Core Data. I have my NSManagedObject classes set up with their dynamic accessors. I perform a fetch that returns several NSManagedObject entity results. Content from each of these entity results (first name, last name) get put into a table view, and then the user picks one out of the table for detailed view and then editing.

The detail view controller receives a pointer to the selected NSManagedObject entity. As the user edits the fields, the corresponding property value in the NSManagedObject entity is updated. This seemed like the cleanest way to manage these changes.

Now, rather than committing the changes using save, I want to provide a cancel-editing feature that rolls back to what is in the data base for that entity. I really only want to restore the one entity and not perform the entire refetch.

I tried rollback and I tried NSUndoManager (with beginUndoGrouping and endUndoGrouping), and that is not working. I don't think I understand what rollback is really supposed to do.

But in any case, I still want to restore the property values in just that single entity (taking the lazy approach to only fetch what is needed, which is the one entity) so that my detail view controller can refill its view with the correct information. Right now it is using the NSManagedObject entity values, which contain the edited values, which were cancelled.

I suppose I could just start the edit process by creating a copy of the NSManagedObject. If the cancel-editing button is pressed, I could copy it back into the original. (I might even be able to just replace the original with the copy by moving the pointer. But since the pointer has actually been passed through several objects, I'm not sure how to manage the retain number on the c开发者_开发知识库opy.)

Does anyone have any other suggestions?

Thanks

Using rollback should accomplish what you want and I'm not sure what it doesn't. It is probably an implementation detail error.

You can find the specific managed object/s that were updated but not yet saved by calling the context's updatedObjects.