Sum all numbers of all the cells in tableview ios - ios

Question

I am looking how to make a sum of all the cells in my tableview.
Each cell crated by user have a number on a label. This number is diferent in each cell.
How can i make the sum of all the numbers in all the cells?
I think its important to say im using Core Data.
Thanks, hope anyone can help me.
Be free to ask any other detail.
EDIT:
#synthesize fetchedResultsController = __fetchedResultsController;
#synthesize managedObjectContext = __managedObjectContext;
#synthesize selectedYear;
- (void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
self.view.backgroundColor = [UIColor colorWithPatternImage:[UIImage imageNamed:#"fondo.png"]];
self.navigationItem.leftBarButtonItem = self.editButtonItem;
[self.tableView setSeparatorColor:[UIColor brownColor]];
}
- (void)setupFetchedResultsController
{
// 1 - Decide what Entity you want
NSString *entityName = #"Years"; // Put your entity name here
NSLog(#"Setting up a Fetched Results Controller for the Entity named %#", entityName);
// 2 - Request that Entity
NSFetchRequest *request = [NSFetchRequest fetchRequestWithEntityName:entityName];
// 3 - Filter it if you want
//request.predicate = [NSPredicate predicateWithFormat:#"Years.name = Blah"];
// 4 - Sort it if you want
request.sortDescriptors = [NSArray arrayWithObject:[NSSortDescriptor sortDescriptorWithKey:#"subject"
ascending:YES
selector:#selector(localizedCaseInsensitiveCompare:)]];
// 5 - Fetch it
self.fetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:request
managedObjectContext:self.managedObjectContext
sectionNameKeyPath:nil
cacheName:nil];
[self performFetch];
}
- (void)viewWillAppear:(BOOL)animated
{
[super viewWillAppear:animated];
[self setupFetchedResultsController];
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *CellIdentifier = #"My Cell";
MarksCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil) {
cell = [[MarksCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier];
}
Year *years = [self.fetchedResultsController objectAtIndexPath:indexPath];
cell.celltitlelabel.text = years.subject;
return cell;
}

Answer 1

Assuming that the Year entity has an attribute value which is an NSNumber:
NSArray *myNumbers = self.fetchedResultsController.fetchedObjects;
NSNumber *sum = [myNumbers valueForKeyPath:#"#sum.value"];