- (void)viewWillTransitionToSize:(CGSize)size withTransitionCoordinator:(id<UIViewControllerTransitionCoordinator>)coordinator

func viewWillTransitionToSize(_ size: CGSize,
    withTransitionCoordinator coordinator: UIViewControllerTransitionCoordinator)

NotificationCenter.default.addObserver(self, selector: #selector(orientationChanged), name:  Notification.Name("UIDeviceOrientationDidChangeNotification"), object: nil)

@objc func orientationChanged() {

    if(UIDeviceOrientationIsLandscape(UIDevice.current.orientation)){

        print("landscape")
    }

    if(UIDeviceOrientationIsPortrait(UIDevice.current.orientation)){

        print("Portrait")
    }

}