Implementing Undo for a Cut operation, against an NSManagedObject

FROM : Neil Clayton
DATE : Sat Jun 24 13:51:48 2006

Hi,
I'd like to be able to nicely undo a cut operation, for a managed 
coredata object.

My initial idea was something like this (where Preset is the managed 
object):

- (void) addPresetBack:(Preset*)preset {
   [presetsController insert:preset];
}

- (IBAction) cut:(id)sender {
   Preset *preset = [presetsController selectedObject];
   [self copy:self]; // store some interesting data in pasteboard
   NSUndoManager *undo = [self undoManager];
   [[undo prepareWithInvocationTarget:self] addPresetBack:preset];
   if(![undo isUndoing]) {
       [undo setActionName:NSLocalizedString(@"Cut", @"Cut")];
   }
   [presetsController removeObject:preset];
}

But I'm finding (probably quite sensible) that the preset is dead/
empty once I get back to addPresetBack.  This makes sense, since 
removing it from the NSArrayController probably causes the object to 
be deleted from the current DB.  Thus, when Undo is called, I end up 
inserting a blank object.

What's the recommended way to handle cut/undo style operations with 
CoreData?

---
Neil Clayton