CoreData: Clear changes from NSManagedObjectContext

Question

I'm instantiating a NSManagedObjectContext object at the Application delegate level and sharing it across all my UIViewControllers. Here's the code that I use to access it in one of my View Controllers:

        NSManagedObjectContext *managedObjectContext = appDelegate.managedObjectContext;
        modelObj = (Model *) [NSEntityDescription insertNewObjectForEntityForName:@"Model" inManagedObjectContext:[appDelegate managedObjectContext]];

Now in this screen, I have a UITableView with 9 rows & each cell has a UITextField. As the user inputs values into the textfields, I assign them into modelObj. Now, my user has an option to cancel out and discard all the changes or save them to disk. I have the save code working fine. But in the case when a user tries to discard the changes, I'm not sure what to do. There doesn't seem to be a [managedObjectContext discardChanges] method to throw them all away.

I can think of a couple of ways of solving this.

• Create a new instance of NSManagedObjectContext for each controller instead of sharing one across the application.
• Or, I could create a bunch of NSStrings in my code and save user values in them and call insertNewObjectForEntityForName: only if the user clicks save.

Which way is the right one? Or is there a way to make NSManagedObjectConext discard all the changes that were made to it?

Thanks,
Teja.

Answer 1

NSManagedObjectContext has a simple method for this:

[managedObjectContext rollback];

This method "removes everything from the undo stack, discards all insertions and deletions, and restores updated objects to their last committed values." (documentation)

Unless I'm missing something, that should give you everything you need.