save/load TextField after it has been edited - iphone

Question

I have this app with a TextField and a Save Button that I want to save when I close after it has been edited and load when I open but I cannot figure it out.
I have written something but when I try to start there comes always the
error: "Fatal 1: Fatal error: Unexpectedly found nil while unwrapping
an Optional value"
This is the code (that is in the my ViewController) but I don't know if its the best way to do it:
#IBOutlet weak var numText: UITextField!
override func viewDidLoad() {
super.viewDidLoad()
if UserDefaults.standard.object(forKey: "num") == nil {
numText.text = "15"
}
else {
let number = UserDefaults.standard.object(forKey: "num") as! String
numText.text = number
}
// Do any additional setup after loading the view, typically from a nib.
}
#IBAction func saveButtonPressed(_ sender: UIButton) {
if numText.text == nil {
UserDefaults.standard.set("15", forKey: "num")
}
else {
UserDefaults.standard.set(numText.text, forKey: "num")
}
}

Answer 1

Add the text as a computed Property in the ViewController:
var SAVEDTEXTKEY = "num"
var savedText: String? {
set{
guard let value = newValue else {
UserDefaults.standard.removeObject(forKey: SAVEDTEXTKEY)
UserDefaults.standard.synchronize()
return
}
UserDefaults.standard.set(value, forKey: SAVEDTEXTKEY)
UserDefaults.standard.synchronize()
}
get{
return UserDefaults.standard.string(forKey: SAVEDTEXTKEY)
}
}
After that, when you want to save just do :
self.savedText = self.numText?.text
And when you want to retrieve it just do:
self.numText.text = self.savedText
The problem I think is that you're not calling
UserDefaults.standard.synchronize()
after setting the value in user defaults.