Change status bar color dynamically in Swift 4

I hope below code will use for your need (for Swift4):

override func viewDidLoad() {
    super.viewDidLoad()

    let statusBar = UIApplication.shared.value(forKey: "statusBar") as? UIView
    if statusBar?.responds(to: #selector(setter: UIView.backgroundColor)) ?? false {
        statusBar?.backgroundColor = .green
    }
}

Alternatively, you could try this:

   if let StatusbarView = UIApplication.shared.value(forKey: "statusBar") as? UIView {
                StatusbarView.backgroundColor = .green
   }

Create a property with type UIStatusBarStyle and return the value in preferredStatusBarStyle

And you can change its value whenever you need and call setNeedsStatusBarAppearanceUpdate()

class ViewController: UIViewController {

    override var preferredStatusBarStyle: UIStatusBarStyle {
        return self.style
    }
    var style:UIStatusBarStyle = .default

    override func viewDidLoad() {
        super.viewDidLoad()
    }

    @IBAction func changeStyle(_ sender: UIButton) {
        if self.style == .lightContent {
            self.style = .default
        } else {
            self.style = .lightContent
        }
        setNeedsStatusBarAppearanceUpdate()
    }
}

override var preferredStatusBarStyle: UIStatusBarStyle { return self.style }

wont be called if you have embedded your view controller in a navigation controller You should change bar style of your navigation controller

self.navigationController?.navigationBar.barStyle = //newStyle

Override preferredStatusBarStyle and call setNeedsStatusBarAppearanceUpdate() when it needs an update. In my example I used a simple dark mode controlled by a boolean property useDarkMode. As soon as it gets changed the UI is updated (including the status bar):

var useDarkMode = false {
    didSet {
        if useDarkMode != oldValue {
            updateUI()
        }
    }
}

private func updateUI() {
    UIView.animate(withDuration: 0.25) {
        if self.useDarkMode {
            self.view.backgroundColor = .darkGray
            self.view.tintColor = .white
        } else {
            self.view.backgroundColor = .white
            self.view.tintColor = nil
        }

        self.setNeedsStatusBarAppearanceUpdate()
    }
}

override var preferredStatusBarStyle: UIStatusBarStyle {
    return useDarkMode ? .lightContent : .default
}