Undo Management with Core Data

Question

I\'m trying to implement undo support using Core Data on the iPhone and I ran into a few problems.

I currently have a couple of managed objects set up but when I make ch

Answer 1

While the undo features will work pretty much out of the box, you do need to allocate an NSUndoManager for the NSManagedObjectContext for which you want undo support.

The easiest way to do this is to set up the undo support when something asks your appDelegate for the NSManagedObjectContext

This is the default method that apple gives you:

- (NSManagedObjectContext *) managedObjectContext {

    if (managedObjectContext != nil) {
        return managedObjectContext;
    }

    NSPersistentStoreCoordinator *coordinator = [self persistentStoreCoordinator];
    if (coordinator != nil) {
        managedObjectContext = [[NSManagedObjectContext alloc] init];

        [managedObjectContext setPersistentStoreCoordinator: coordinator];
    }
    return managedObjectContext;
}

Modify it to look like this:

- (NSManagedObjectContext *) managedObjectContext {

    if (managedObjectContext != nil) {
        return managedObjectContext;
    }

    NSPersistentStoreCoordinator *coordinator = [self persistentStoreCoordinator];
    if (coordinator != nil) {
        managedObjectContext = [[NSManagedObjectContext alloc] init];

        //Undo Support
        NSUndoManager *anUndoManager = [[NSUndoManager  alloc] init];
        [managedObjectContext setUndoManager:anUndoManager];
        [anUndoManager release];

        [managedObjectContext setPersistentStoreCoordinator: coordinator];
    }
    return managedObjectContext;
}