UIView frame not updating after orientation change

Add this function and you´ll detect the orientation change:

override func viewWillTransition(to size: CGSize, with coordinator: UIViewControllerTransitionCoordinator) {
    if UIDevice.current.orientation.isLandscape {
        print("Landscape")
    } else if UIDevice.current.orientation.isPortrait {
        print("Portrait")
    }
}

To get orientation change callback you need to add this Notification

NotificationCenter.default.addObserver(self, selector: #selector(ViewController.rotated), name: NSNotification.Name.UIDeviceOrientationDidChange, object: nil)

and you need to implement this method

func rotated() {
    if(UIDeviceOrientationIsLandscape(UIDevice.current.orientation))
    {
        print("landscape")
    }

    if(UIDeviceOrientationIsPortrait(UIDevice.current.orientation))
    {
        print("Portrait")
    }
}

The above accepted answer returns frame size before transition.So your view is not updating..You need to get the frame size after the transition has been completed.

override func viewWillTransition(to size: CGSize, with coordinator: UIViewControllerTransitionCoordinator) {

        coordinator.animate(alongsideTransition: { (UIViewControllerTransitionCoordinatorContext) -> Void in

            let orient = UIApplication.shared.statusBarOrientation

            switch orient {

            case .portrait:

                print("Portrait")

            case .landscapeLeft,.landscapeRight :

                print("Landscape")

            default:

                print("Anything But Portrait")
            }

            }, completion: { (UIViewControllerTransitionCoordinatorContext) -> Void in
                //refresh view once rotation is completed not in will transition as it returns incorrect frame size.Refresh here           

        })
        super.viewWillTransition(to: size, with: coordinator)

    }