NSManagedObjectContext: undo save-operation?

Question

I'd like to undo a save-operation on my NSManagedObjectContext; I always thought, that's what the NSUndoManager is for, but it seems as if undoing over a save-operation doesn't work...

An example:

[[NSManagedObjectContext MR_contextForCurrentThread] setUndoManager:[NSUndoManager new]];
[[NSManagedObjectContext MR_contextForCurrentThread].undoManager beginUndoGrouping];
MyDataObject *mdo = [MyDataObject MR_createInContext:[NSManagedObjectContext MR_contextForCurrentThread]];
mdo.name = @"...";
[[NSManagedObjectContext MR_contextForCurrentThread] save:nil];
[[NSManagedObjectContext MR_contextForCurrentThread].undoManager endUndoGrouping];
[[NSManagedObjectContext MR_contextForCurrentThread].undoManager undo];

But the insertion is not undone... is there no way to achieve this? Like a transaction?

Answer 1

Could you use a child managed object context to do your save (which pushes it up to the parent, but doesn't touch the file on disk), and then do a rollback on the parent if you want to undo it?

I think calling save is like committing all the changes you've made since the last save, and rollback is like discarding them. Once you've committed the changes, they're in the persistent store and there's nothing keeping transaction logs in order to support rolling back.

Can you explain a bit more about why you want a save in the middle of your transaction?