How to Update existing objects in Core Data?

Question

I'd like to update an object in Core Data. This is my code:

var detailTaskModel: TaskModel!
detailTaskModel.date = dateFromDP         //update value

let appDelegate = (UIApplication.sharedApplication().delegate as AppDelegate)
appDelegate.saveContext()

I'm using a NSFetchedResultsController and Swift.

Update:

var fetchedResultsController: NSFetchedResultsController = NSFetchedResultsController()

My func for loading the CoreData data:

func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {

    var cell: TaskCell = tableView.dequeueReusableCellWithIdentifier("myCell") as TaskCell

    let thisTask = fetchedResultsController.objectAtIndexPath(indexPath) as TaskModel
    cell.textLabel?.text = thisTask.task
    return cell
}

Saving CoreData:

let appDelegate = (UIApplication.sharedApplication().delegate as AppDelegate)
let entityDescription = NSEntityDescription.entityForName("TaskModel", inManagedObjectContext: managedObjectContext!)
let task = TaskModel(entity: entityDescription!, insertIntoManagedObjectContext: managedObjectContext!)
task.task = labelText

Answer 1

You simply update any property of Core data object and call save on NSManagedObjectContext. You can also check for any changes with hasChanges method.

 managedObject.setValue("newValue", forKey: "propertyName") 

Update your object like above or direct call assignment and do the following

if let moc = self.managedObjectContext {
   var error: NSError? = nil
   if moc.hasChanges {
       !moc.save(&error)
   }
}