用户默认设置不起作用

Question

Can someone help me why I can't perform the nsuserdefaults correctly. When I try to tapped save it does nothing. What i want is when i tapped saved it will saved to the phone and then when i try to go back to the viewcontroller again it will appear. Here is my code below.

override func viewDidLoad() {
    super.viewDidLoad()

    self.navigationItem.setHidesBackButton(true, animated: false)
    self.hideKeyboardWhenTappedAround()

    firstName.delegate = self
    lastName.delegate = self

    tableView.reloadData()

    //Save Defaults
    let defaults = UserDefaults.standard
    if let _ = defaults.object(forKey: "firstName") as? String {
        self.firstName.text = defaults.object(forKey: "firstName") as? String
    }

    if let _ = defaults.object(forKey: "lastName") as? String {
        self.lastName.text = defaults.object(forKey: "lastName") as? String
    }

    if let _ = defaults.object(forKey: "contacts") as? Array<Any> {
        self.contacts = (defaults.object(forKey: "contacts") as? Array)!
    }
}



 //MARK -> SAVE BUTTON
    @IBAction func saveButtonSelected(_ sender: AnyObject) {
            let defaults: UserDefaults = UserDefaults.standard
            defaults.set(self.firstName.text, forKey: "firstName")
            defaults.set(self.lastName.text, forKey: "lastName")
            defaults.set(contacts, forKey: "contacts")
        }

Answer 1

Try this:

 @IBAction func saveButtonSelected(_ sender: AnyObject) {
                let defaults: UserDefaults = UserDefaults.standard
                defaults.set(self.firstName.text, forKey: "firstName")
                defaults.set(self.lastName.text, forKey: "lastName")
                defaults.set(contacts, forKey: "contacts")
                defaults.synchronize()
            }