如何更新CoreData中对象的值？

Question

I'm sort of new to programming with CoreData, so I have no idea how to go about doing this. I'm trying to update a string that's being stored in a CoreData object, but I have not the faintest idea on how to do that. Here's my code:

Here's where I make the new object:

- (void)insertNewObject:(id)sender
{
     self.steakName = @"No Name";
     NSManagedObjectContext *context = [self.fetchedResultsController managedObjectContext];
     NSEntityDescription *entity = [[self.fetchedResultsController fetchRequest] entity];
     NSManagedObject *newManagedObject = [NSEntityDescription      insertNewObjectForEntityForName:[entity name] inManagedObjectContext:context];

     [newManagedObject setValue:self.steakName forKey:@"steakName"];

     // Save the context.
     NSError *error = nil;
     if (![context save:&error]) {
         NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
         abort();
     }
}

Here's where I want to update it: (It's being updated in a different class then where it's being made.)

- (IBAction)update:(id)sender {
    MasterViewController *masterViewController = [[MasterViewController alloc] init];
    masterViewController.steakName = [self.steakNameTextField text];
    self.detailDescriptionLabel.text = masterViewController.steakName;
    NSLog(masterViewController.steakName);
}

Thank you for your help! :)

Answer 1

You do it almost the same way you would without Core Data. Keep a reference to the object as a property in the class where it's created and make whatever changes you want. The only difference is, when you want the changes to persist, you save your context again.