How to pass a custom property between view controller using NSManagedObject object?

Question

I'm working on a simple notes app, and I created an entity called "Note" in the data model that have only one attribute that named "content" of type nsstring.

Now I careated a Note class using editor/create NSManagedObject subclass from the data model section.

In my create notes view controller i'm saving the data to the database in the prepareForSegue method that looks like this:

@implementation NOCreateNotesViewController

- (NSManagedObjectContext *) managedObjectContext
{
    NSManagedObjectContext *context = nil;

    id delegate = [[UIApplication sharedApplication] delegate];

    if ([delegate performSelector:@selector(managedObjectContext)]) {
        context = [delegate managedObjectContext];
    }

    return context;
}


- (void) prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
    if (sender != self.saveButton) return;
    if (self.noteText.text.length > 0) {
        self.note = [[Note alloc] init];
        self.note.content = self.noteText.text;
    }

    NSManagedObjectContext * context = [self managedObjectContext];

    // creating a new managed object

    NSManagedObject *newNote = [NSEntityDescription insertNewObjectForEntityForName:@"Note" inManagedObjectContext:context];

    [newNote setValue:self.noteText.text forKey:@"content"];

    NSError * error = nil;

    if ([context save:&error]) {
        NSLog(@"Can't Save! %@ %@", error, [error localizedDescription]);
    }
}

But not I want to pass the object that a user wants to edit (meaning the note in the selected row from the table view) this way:

- (void) prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
    if ([segue.identifier isEqualToString:@"editeNote"]) {
        NSManagedObject * selectedNote = [self.notes objectAtIndex:[self.tableView indexPathForSelectedRow].row];
        NOCreateNotesViewController * destination = [segue destinationViewController];
        destination.note = selectedNote;
    }
}

And obviously I can't pass a Note object with a pointer to NSManagedObject...this is because I want to update my Note entity if this is an editing segue instead of creating a new one.

In the tutorial I learned core data basics from they teach with just creating objects on the fly and note using a custom class for the objects with editor/create NSManagedObject subclass so i'm getting a bit confused..

Please help

Nick Nick · Accepted Answer · 2014-04-17T14:18:25

NSManagedObject * selectedNote = [self.notes objectAtIndex:[self.tableView indexPathForSelectedRow].row];

wants to be:

Note * selectedNote = [self.notes objectAtIndex:[self.tableView indexPathForSelectedRow].row];

Why are you saving the data to your model in prepareForSegue:? Surely you have a Save or Done button in the view?

How to pass a custom property between view controller using NSManagedObject object?

1 Answers