private func getRootViewController() -> UIViewController? {
    var rootViewController = UIApplication.shared.keyWindow?.rootViewController
    if let navigationController = rootViewController as? UINavigationController {
        rootViewController = navigationController.viewControllers.first
    }
    if let tabBarController = rootViewController as? UITabBarController {
        rootViewController = tabBarController.selectedViewController
    }
    return rootViewController
}


// -- Alternative solution 

var topVC = UIApplication.sharedApplication().keyWindow?.rootViewController
while((topVC!.presentedViewController) != nil) {
     topVC = topVC!.presentedViewController
}