ProgressView.swift

import UIKit
import PlaygroundSupport

class TestViewController : UIViewController {
	
	let btn: UIButton = {
		let b = UIButton()
		b.translatesAutoresizingMaskIntoConstraints = false
		b.setTitle("Tap Me", for: .normal)
		b.backgroundColor = .red
		return b
	}()
	
	let theProgressView: UIProgressView = {
		let v = UIProgressView()
		v.translatesAutoresizingMaskIntoConstraints = false
		return v
	}()
	
	override func viewDidLoad() {
		super.viewDidLoad()
		
		view.addSubview(btn)
		
		btn.addTarget(self, action: #selector(didTap(_:)), for: .touchUpInside)
		
		btn.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = true
		btn.topAnchor.constraint(equalTo: view.topAnchor, constant: 20.0).isActive = true
		
		view.addSubview(theProgressView)
		
		theProgressView.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = true
		theProgressView.topAnchor.constraint(equalTo: btn.bottomAnchor, constant: 40.0).isActive = true

		theProgressView.widthAnchor.constraint(equalToConstant: 100.0).isActive = true
		
		theProgressView.progress = 0.0
		
	}
	
	@objc func didTap(_ sender: Any?) -> Void {
		theProgressView.progress += 0.01

		DispatchQueue.main.async {
			print(self.theProgressView.progress)
			for v in self.theProgressView.subviews {
				print(v)
			}
		}

	}
	
}


let vc = TestViewController()
vc.view.backgroundColor = .white
PlaygroundPage.current.liveView = vc