Useful UIViewController extenstion for simple alert call with just message: String? parameter.

ExtensionUIViewController.swift

extension UIViewController {
    func showSimpleAlert(message: String?) {
        let alert = UIAlertController(title: "Note", message: message, preferredStyle: .alert)
        alert.addAction(UIAlertAction(title: "Ok", style: .default, handler: nil))
        self.present(alert, animated: true, completion: nil)
    }
}