/// An extension to traverse the responder chain for the nearest parent view controller.
extension UIView {

    /// The nearest parent view controller in the responder chain.
    var parentViewController: UIViewController? {
        if let nextResponder = self.next as? UIViewController {
            return nextResponder
        } else if let nextResponder = self.next as? UIView {
            return nextResponder.parentViewController
        } else {
            return nil
        }
    }

}