Remove Values Which Are Nil From NSManagedObject - swift

Question

I had an issue where my core data NSManagedObject always had nil values inside of it on the first run of the application. Do overcome this I thought I would attempt to check for nil values and remove them in case they are found. My attempted code is as follow:
do {
let results = try managedContext.fetch(fetchRequest)
scoreData = results as! [NSManagedObject]
print(scoreData)
for result in results as! [NSManagedObject] {
if result.value(forKey: "name") as? String == nil || result.value(forKey: "date") as? String == nil || result.value(forKey: "score") as? String == nil {
managedContext.delete(result.value(forKey: "name") as! NSManagedObject)
managedContext.delete(result.value(forKey: "date") as! NSManagedObject)
managedContext.delete(result.value(forKey: "score") as! NSManagedObject)
} else {
name = result.value(forKey: "name") as! String
date = result.value(forKey: "date") as! String
score = result.value(forKey: "score") as! Int
}
The line of code 'managedContext.delete()' is giving me a hard time as it isnt properly working. Am I using a wrong method or is my code just incorrect. Any help welcome.
class LeaderboardTableVC: UITableViewController {
var finishedGame = 0
var gameScore:Int! = 0
var name:String!
var date:String!
var score:Int!
var scoreData = [NSManagedObject]()
override func viewDidLoad() {
super.viewDidLoad()
if finishedGame == 1{
saveNew()
}
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
}
func saveNew(){
let appDelegate = UIApplication.shared.delegate as! AppDelegate
let managedContext = appDelegate.persistentContainer.viewContext
let entity = NSEntityDescription.entity(forEntityName: "Scores", in: managedContext)
let object = NSManagedObject(entity: entity!, insertInto: managedContext)
let enterNameAlert = UIAlertController(title: "Please Enter Your Name", message: "This will be used to place you in the leaderboards", preferredStyle: .alert)
enterNameAlert.addTextField { (textField:UITextField) -> Void in
textField.placeholder = "Name"
textField.autocapitalizationType = UITextAutocapitalizationType.words
textField.autocorrectionType = UITextAutocorrectionType.no
textField.clearsOnBeginEditing = true
textField.clearsOnInsertion = true
textField.clearButtonMode = UITextFieldViewMode.always
textField.keyboardType = UIKeyboardType.default
}
let cancelAction = UIAlertAction(title: "Cancel", style: .cancel, handler: nil)
let confirmAction = UIAlertAction(title: "Confirm", style: .default) { (action:UIAlertAction) in
let currentTime = Date()
let timeFormatter = DateFormatter()
timeFormatter.locale = Locale.current
timeFormatter.dateFormat = "HH:mm dd/MM/yy"
let convertedTime = timeFormatter.string(from: currentTime)
let enteredName = enterNameAlert.textFields?.first?.text
object.setValue(convertedTime, forKey: "date")
object.setValue(self.gameScore, forKey: "score")
object.setValue(enteredName, forKey: "name")
do {
try managedContext.save()
self.scoreData.append(object)
self.tableView.reloadData()
} catch let error as NSError {
print("Could not save \(error), \(error.userInfo)")
}
}
enterNameAlert.addAction(cancelAction)
enterNameAlert.addAction(confirmAction)
self.present(enterNameAlert, animated: true, completion: nil)
}
override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCell(withIdentifier: "cell") as! LeaderBoardCell
let data = scoreData[(indexPath as NSIndexPath).row]
if data.value(forKey: "date") as? String == nil || data.value(forKey: "score") as? Int == nil || data.value(forKey: "name") as? String == nil {
print("Nil Value")
} else {
cell.dateLabel?.text = "Date: \((data.value(forKey: "date")) as! String)"
cell.dateLabel.adjustsFontSizeToFitWidth = true
cell.scoreLabel?.text = "Score: \((data.value(forKey: "score")) as! Int)"
cell.scoreLabel.adjustsFontSizeToFitWidth = true
cell.nameLabel?.text = "Name: \((data.value(forKey: "name")) as! String)"
cell.nameLabel.adjustsFontSizeToFitWidth = true
}
return cell
}
Thanks

Answer 1

you can simply check for value if there is a value then store it to the variable as below. try the below code.
for result in results as! [NSManagedObject] {
if let name = result.value(forKey: "name") {
self.name = name as! String // if there will be a value in result for key 'name' then it will sore it. otherwise it won't let it be inside the if condition.
}
if let date = result.value(forKey: "date") {
self.date = date as! String
}
if let score = result.value(forKey: "score") {
self.score = score as! Int
}
}

Answer 2

So your problem is that the properties of the managed object are nil, eg they don't exist. Trying to delete the values won't do anything as they already don't exist. Instead you can delete the managed object, like this:
do {
let results = try managedContext.fetch(fetchRequest)
scoreData = results as! [NSManagedObject]
print(scoreData)
for result in results as! [NSManagedObject] {
if result.value(forKey: "name") as? String == nil || result.value(forKey: "date") as? String == nil || result.value(forKey: "score") as? String == nil {
managedContext.delete(result)
} else {
name = result.value(forKey: "name") as! String
date = result.value(forKey: "date") as! String
score = result.value(forKey: "score") as! Int
}
(Don't forget to save the managed context after)
Be careful though! If you have relationships in your model and you delete a managed object the relationship will still exist, meaning when you access the relationship objects there will be nil objects (the ones you delete here)
Edit: to ensure that your tableView is in sync with your dataSource (scoreData) add a didSet function to your variable declaration like so:
var scoreData = [NSManagedObject]() {
didSet {
tableView.reloadData()
}
}
This means that every time you change scoreData the tableView is reloaded (you don't need to reload data in your saveNew function anymore with this)