• Labels
• Text fields
• Buttons

• Select
• Make it full size
• Editor -> Resolve Auto Layout Issues -> Adding Missing Constraint

If text fields appear near the top of the screen, then the virtual keyboard can slide up. 
However, if the text fields appear too close to the bottom of the screen,  your app needs 
to slide its view up to keep the text field visible while allowing the virtual keyboard to 
fill the bottom of the screen.

• Textfield in the center, SE won't show keyboard (XR will)
• Keyboard won't go away automatically
• Dismiss keyboard not easy and here

Right Drag to declare  @IBOutlet weak var vv_field: UITextField!

override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.

    let tap = UITapGestureRecognizer(target: self, action:
            #selector(cf_dismissKeyboard))
        view.addGestureRecognizer(tap)
    }
    
    @objc func cf_dismissKeyboard (_ sender: UITapGestureRecognizer) {
        vv_field.resignFirstResponder()
        
    }

    @IBAction func cf_changeBtnText(_ sender: UIButton) {
       //sender.setTitle("Display", for: .normal)
        if (sender.title(for: .normal) == "Button") {
            sender.setTitle("Display", for: .normal)
        }
        else {
            sender.setTitle("Button", for: .normal)
        }
    }

• Two labels and one slider
• Slider changes label font size
• Slider Min 6, Max 72, Init 18
• Tricky: constraints

      override func viewDidLoad() {
          super.viewDidLoad()
          let value = vv_slider.value
          vv_output.font = vv_output.font.withSize(CGFloat(value))
          vv_value.text = "\( Int(value) )"
      }
  
      @IBOutlet weak var vv_slider: UISlider!
      @IBOutlet weak var vv_output: UILabel!
      @IBOutlet weak var vv_value: UILabel!
      
      @IBAction func cf_update(_ sender: UISlider) {
          let value = Int(sender.value)
          vv_value.text = "\( value )"
          vv_output.font = vv_output.font.withSize(CGFloat(value))
      }
  

    

• Three buttons, one switch
• Button change either button or view background color
• Switch off resets

class ViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.
        vv_btnRed.setTitleColor(UIColor.red, for: .normal)
        vv_btnGreen.setTitleColor(UIColor.green, for: .normal)
        vv_btnBlue.setTitleColor(UIColor.blue, for: .normal)
    }

    @IBOutlet weak var vv_switch: UISwitch!
    @IBOutlet weak var vv_label: UILabel!
    
    @IBOutlet weak var vv_btnRed: UIButton!
    @IBOutlet weak var vv_btnGreen: UIButton!
    @IBOutlet weak var vv_btnBlue: UIButton!
    
    @IBAction func cf_changeColor(_ sender: UIButton) {
        if (vv_switch.isOn) {
            switch sender.tag {
            case 1: self.view.backgroundColor = UIColor.red
            case 2: self.view.backgroundColor = UIColor.green
            case 3: self.view.backgroundColor = UIColor.blue
			default: break
            }
        }
        else {
            switch sender.tag {
            case 1: vv_btnRed.backgroundColor = UIColor.red
            case 2: vv_btnGreen.backgroundColor = UIColor.green
            case 3: vv_btnBlue.backgroundColor = UIColor.blue
			default: break
            }
        }
    }
    
    @IBAction func cf_reset(_ sender: UISwitch) {
        if ( !sender.isOn ) {
            vv_btnRed.setTitleColor(UIColor.red, for: .normal)
            vv_btnGreen.setTitleColor(UIColor.green, for: .normal)
            vv_btnBlue.setTitleColor(UIColor.blue, for: .normal)

            vv_btnRed.backgroundColor = UIColor.white
            vv_btnGreen.backgroundColor = UIColor.white
            vv_btnBlue.backgroundColor = UIColor.white
            self.view.backgroundColor = UIColor.white
        }
    }
}