Get currently active view controller

gistfile1.txt

fileprivate func getShowingViewController(_ rootViewController: UIViewController) -> UIViewController? {
    var isRoot = false
    var showViewController: UIViewController? = rootViewController
    while (!isRoot) {
        if let tempViewController = showViewController?.presentedViewController {
            showViewController = tempViewController
        } else {
            isRoot = true
        }
    }
    return showViewController
}