extension UIViewController {

    func supportedInterfaceOrientations() -> UIInterfaceOrientationMask {
        if let nvc = self as? UINavigationController {
            return nvc.topViewController!.supportedInterfaceOrientations()
        } else {
            return .Portrait
        }
    }

    func shouldAutorotate() -> Bool {
        if let nvc = self as? UINavigationController {
            return nvc.topViewController!.shouldAutorotate()
        } else {
            return false
        }
    }

    func preferredInterfaceOrientationForPresentation() -> UIInterfaceOrientation {
        if let nvc = self as? UINavigationController {
            return nvc.topViewController!.preferredInterfaceOrientationForPresentation()
        }  else {
            return .Portrait
        }
    }
}