@IBOutlet weak var vv_cntLabel: UILabel!

@IBOutlet weak var vv_startItem: UIBarButtonItem!
@IBOutlet weak var vv_stopItem: UIBarButtonItem!

vv_cntLabel.layer.cornerRadius = 20
vv_cntLabel.layer.borderWidth = 5
vv_cntLabel.layer.borderColor = UIColor.orange.cgColor
vv_cntLabel.layer.backgroundColor = UIColor.green.cgColor

Swift 3, Xcode 8.3	CALayer extension

Swift 4, Xcode 9.2 - Use IBDesignable and IBInspectable

class ViewController: UIViewController {
    var cv_timer : NSTimer = NSTimer()
    var cv_counter : NSInteger = 0

@IBAction func cf_startCnt(_ sender: UIBarButtonItem) {
	cv_timer = Timer.scheduledTimer(timeInterval: 0.2, target: self, 
	selector: #selector(cfp_updateCnt), userInfo: nil, repeats: true);
}
    
@objc func cfp_updateCnt() {
	cv_counter = cv_counter+1
	vv_cntLabel.text = String(cv_counter)
}

let string = "abc"
// Pad at end
string.padding(toLength: 7, withPad: "X", startingAt: 0)
// "abcXXXX"    

// Pad at start
String(String(string.reversed()).padding(toLength: 7, withPad: "X", startingAt: 0).reversed())
// "XXXXabc" 

class ViewController: UIViewController {
    var cv_timer : Timer = Timer()
    var cv_counter : NSInteger = 0

    override func viewDidLoad() {
        super.viewDidLoad()
        //vv_stopItem.isEnabled = false
        vv_cntLabel.layer.cornerRadius = 20
        vv_cntLabel.layer.borderWidth = 5
        vv_cntLabel.layer.borderColor = UIColor.orange.cgColor
        vv_cntLabel.layer.backgroundColor = UIColor.green.cgColor
    }

    @IBOutlet weak var vv_cntLabel: UILabel!
    @IBOutlet weak var vv_startItem: UIBarButtonItem!
    @IBOutlet weak var vv_stopItem: UIBarButtonItem!
    
    @IBAction func cf_startCnt(_ sender: UIBarButtonItem) {
        cv_timer = Timer.scheduledTimer(timeInterval: 0.2, target: self, selector: 
			#selector(cfp_updateCnt), userInfo: nil, repeats: true);
        sender.isEnabled = false
        vv_stopItem.isEnabled = true
    }
    
    @IBAction func cf_stopCnt(_ sender: UIBarButtonItem) {
        cv_timer.invalidate()
        sender.isEnabled = false
        vv_startItem.isEnabled = true
    }
    
    @IBAction func cf_clearCnt(_ sender: UIBarButtonItem) {
        cv_timer.invalidate()
        cv_counter = 0
        vv_cntLabel.text = "000"
        vv_startItem.isEnabled = true
        vv_stopItem.isEnabled = false
    }

    @objc func cfp_updateCnt() {
        cv_counter = cv_counter+1
        let str = String(cv_counter)
        vv_cntLabel.text = String(String(str.reversed()).padding(toLength: 3, 
			withPad: "0", startingAt: 0).reversed())
    }
}

• ver01 - image click then text to speech
• StackOverflow
• AppCoda
• TutsPlus

import AVFoundation

let cv_speechSynthesizer = AVSpeechSynthesizer()
let lv_myUtterance = AVSpeechUtterance(string: "You are facing")
cv_speechSynthesizer.speak(lv_myUtterance)

import UIKit
import AVFoundation

class ViewController: UIViewController {
    var cv_speechSynthesizer = AVSpeechSynthesizer()
    
    override func viewDidLoad() {
        super.viewDidLoad()
        let lv_tap = UITapGestureRecognizer(target: self, action: #selector(cf_tapCompass))
        vv_imageView.addGestureRecognizer(lv_tap)
        
        // can be set in GUI - attribute inspector
        vv_imageView.isUserInteractionEnabled = true
    }

    @IBOutlet weak var vv_imageView: UIImageView!
    @IBOutlet weak var vv_label: UILabel!
    
    @objc func cf_tapCompass(gestureRecognizer: UITapGestureRecognizer) {
        
        // if the tapped view is a UIImageView then set it to imageview
        if (gestureRecognizer.view as? UIImageView) != nil {
            // vv_label.text = "You are facing"
            
            let lv_myUtterance = AVSpeechUtterance(string: "You are facing")
            lv_myUtterance.rate = 0.5
            cv_speechSynthesizer.speak(lv_myUtterance)
        }
    }
}

• ver02 - image rotation
• Tutorial

UIView.animate(withDuration: 0.5, animations: {
	self.vv_imageView.transform = CGAffineTransform(rotationAngle: (60.0 * CGFloat(M_PI)) / 180.0)
})

...
    var cv_degree = 0.0
...
            UIView.animate(withDuration: 0.5, animations: {
                self.cv_degree = self.cv_degree + 60.0;
                self.vv_imageView.transform = CGAffineTransform(rotationAngle:
                    ( CGFloat(self.cv_degree) * CGFloat(Double.pi) ) / 180.0)

• ver03 - compass sensor, display degrees
• Tutorial
• Update plist with 2 entries, see
• NO NEED to update plist and location service on

import CoreLocation

        cv_locationManager  = CLLocationManager()
        cv_locationManager.delegate = self

        if CLLocationManager.locationServicesEnabled() {
            cv_locationManager.startUpdatingHeading()
        }
		
    func locationManager(_ manager: CLLocationManager, didUpdateHeading newHeading: CLHeading) {
        let lv_heading = newHeading.magneticHeading
        vv_label.text = "Heading: \(String(format: "%04.1f", lv_heading)) degrees"
        let index = Int(round(lv_heading / 45.0))
        cv_strDirection = cv_strDir[index]
        
        UIView.animate(withDuration: 0.5, animations: {
            self.vv_imageView.transform = CGAffineTransform(rotationAngle: (CGFloat(-lv_heading) * CGFloat(Double.pi)) / 180.0)
        })
    }	

import UIKit
import AVFoundation
import CoreLocation

class ViewController: UIViewController, CLLocationManagerDelegate {
    var cv_speechSynthesizer : AVSpeechSynthesizer!
    var cv_locationManager : CLLocationManager!
    
    var cv_strDirection : String = ""
    var cv_strDir : [String] = ["North","Northeast","East","Southeast","South","Southwest","West","Northwest","North"]
        
    override func viewDidLoad() {
        super.viewDidLoad()
        cv_speechSynthesizer = AVSpeechSynthesizer()
        let lv_tap = UITapGestureRecognizer(target: self, action: #selector(cf_tapCompass))
        vv_imageView.addGestureRecognizer(lv_tap)
        
        // can be set in GUI - attribute inspector
        vv_imageView.isUserInteractionEnabled = true
        
        cv_locationManager  = CLLocationManager()
        cv_locationManager.delegate = self
        ////cv_locationManager.headingFilter = 5;  // 5 degrees
        if CLLocationManager.locationServicesEnabled() {
            cv_locationManager.startUpdatingHeading()
        }
    }

    @IBOutlet weak var vv_imageView: UIImageView!
    @IBOutlet weak var vv_label: UILabel!
    
    @objc func cf_tapCompass(gestureRecognizer: UITapGestureRecognizer) {
        
        // if the tapped view is a UIImageView then set it to imageview
        if (gestureRecognizer.view as? UIImageView) != nil {
            // vv_label.text = "You are facing"
            let lv_myUtterance = AVSpeechUtterance(string: "You are facing \(cv_strDirection)")
            lv_myUtterance.rate = 0.55
            cv_speechSynthesizer.speak(lv_myUtterance)
        }
    }

    func locationManager(_ manager: CLLocationManager, didUpdateHeading newHeading: CLHeading) {
        let lv_heading = newHeading.magneticHeading
        vv_label.text = "Heading: \(String(format: "%04.1f", lv_heading)) degrees"
        let index = Int(round(lv_heading / 45.0))
        cv_strDirection = cv_strDir[index]
        
        UIView.animate(withDuration: 0.5, animations: {
            self.vv_imageView.transform = CGAffineTransform(rotationAngle: (CGFloat(-lv_heading) * CGFloat(Double.pi)) / 180.0)
        })
    }
}

• Add Developer Account
• Set Target IOS Version
• Select Device

If you have multiple objects on a user interface, adding multiple constraints can be clumsy, 
especially if you need to rearrange objects. To simplify putting constraints on individual objects, 
you can organize objects into stacks. This lets you move groups of objects around and place 
constraints on that group rather than on all individual objects in that group.

• Constant
• Priority
• Multiplier