// set this as the Root viewController of a navigation controller

class NavTestVC: UIViewController {
    var navID: Int = 0

    @objc func btnTap(_ sender: Any?) {
        let vc = NavTestVC()
        vc.navID = self.navID + 1
        navigationController?.pushViewController(vc, animated: true)
    }

    override func viewDidLoad() {
        super.viewDidLoad()

        view.backgroundColor = UIColor(white: 0.95, alpha: 1.0)

        var config = UIButton.Configuration.filled()
        config.buttonSize = .medium
        config.cornerStyle = .medium
        config.title = "Push"

        let btnA = UIButton(configuration: config)
        btnA.addAction (
            UIAction { _ in
                self.btnTap(nil)
            }, for: .touchUpInside
        )

        let label = UILabel()

        label.translatesAutoresizingMaskIntoConstraints = false
        view.addSubview(label)
        btnA.translatesAutoresizingMaskIntoConstraints = false
        view.addSubview(btnA)

        let g = view.safeAreaLayoutGuide
        NSLayoutConstraint.activate([
            label.topAnchor.constraint(equalTo: g.topAnchor, constant: 40.0),
            label.centerXAnchor.constraint(equalTo: g.centerXAnchor),
            btnA.topAnchor.constraint(equalTo: label.bottomAnchor, constant: 40.0),
            btnA.centerXAnchor.constraint(equalTo: g.centerXAnchor),
        ])

        label.text = "This navID: \(navID)"
    }

    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)
        print("navID:", navID, #function)
    }
    override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(animated)
        print("navID:", navID, #function)
    }
    override func viewWillDisappear(_ animated: Bool) {
        super.viewWillDisappear(animated)
        print("navID:", navID, #function)
    }

}