static var topMostViewController: UIViewController {
    var viewController: UIViewController = (UIApplication.shared.keyWindow?.rootViewController)!

    while (viewController.presentedViewController != nil){
        viewController = viewController.presentedViewController!
    }

    return viewController
}

static var currentViewController: UIViewController? {
    if let tabBarController = UIViewController.topMostViewController as? UITabBarController {
        if let navigationController = tabBarController.selectedViewController as? UINavigationController {
            return navigationController.viewControllers.first
        } else {
            return tabBarController.selectedViewController
        }
    } else if let navigationController = UIViewController.topMostViewController as? UINavigationController {
        return navigationController.viewControllers.first
    } else {
        return UIViewController.topMostViewController
    }
}