How to Update existing objects in Core Data? [duplicate] - ios

Question

This question already has answers here:
How to update existing object in Core Data?
(5 answers)
Closed 5 years ago.
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)
}
}

Answer 2

Updating an object in CoreData is quite similar to creating a new one.
First you have to fetch your object from CoreData using a fetchRequest. After that you can edit the fetched object and update it's attributes.
After that, just save it back using the managedObjectContext.

Answer 3

You can do this, works for me.
if let container = (UIApplication.shared.delegate as? AppDelegate)?.persistentContainer{
let context = container.viewContext
let fetchRequest = NSFetchRequest<Account>(entityName: "Account")
let name = self.txtAccount.text
fetchRequest.predicate = NSPredicate(format: "name == %#", name!)
do {
let results = try context.fetch(fetchRequest)
if (results.count > 0){
for result in results{
id = result.id
number = result.number
}
actualNumber = (number + 1)
//Update the account balance
let update = results[0]
update.number = actualNumber
try context.save()
return id
}
}catch let error {
print("Error....: \(error)")
}
You don't have to write 'result[0] as! NSManagedObject' because you have the NSFetchRequest of type Account and the constant "update" knows that.