Orientation.swift

/// This module contains useful extensions to the base
/// navigation controllers in respect to managing orientation,
/// as well as adding missing functionality to the sdk types.

import Foundation


func currentOrientation() -> UIInterfaceOrientation {
  return UIApplication.shared.statusBarOrientation
}

extension YourNavigationController {

  override var supportedInterfaceOrientations : UIInterfaceOrientationMask {
    return visibleViewController!.supportedInterfaceOrientations
  }

  override var preferredInterfaceOrientationForPresentation: UIInterfaceOrientation {
    return visibleViewController!.preferredInterfaceOrientationForPresentation
  }

  func adjustOrientationIfNeeded() {
    if self.supportedInterfaceOrientations.misses(currentOrientation()) {
      UIDevice.current
        .setValue(self.preferredInterfaceOrientationForPresentation.rawValue,
                  forKey: "orientation")
    }
  }
}

extension UIInterfaceOrientationMask {
  func supports(_ orientation: UIInterfaceOrientation) -> Bool {
    return (orientation.isLandscape && self.contains(.landscape))
        || (orientation.isPortrait && self.contains(.portrait))
  }

  func misses(_ orientation: UIInterfaceOrientation) -> Bool {
    return !supports(orientation)
  }

  public var description: String {
    switch self {
    case .all:
      return "all"
    case .allButUpsideDown:
      return "allButUpsideDown"
    case .landscape:
      return "landscape"
    case .landscapeLeft:
      return "landscapeLeft"
    case .landscapeRight:
      return "landscapeRight"
    case .portrait:
      return "portrait"
    case .portraitUpsideDown:
      return "portraitUpsideDown"
    default:
      return "Unkown UIInterfaceOrientationMask"
    }
  }
}

extension UIInterfaceOrientation {
  public var description: String {
    switch self {
    case .landscapeLeft:
      return "landscapeLeft"
    case .landscapeRight:
      return "landscapeRight"
    case .portrait:
      return "portrait"
    case .portraitUpsideDown:
      return "portraitUpsideDown"
    case .unknown:
      return "unknown"
    }
  }

  func toMask() -> UIInterfaceOrientationMask {
    return self.isPortrait ? .portrait : .landscape
  }
}


/// iOS v9.* has a bug that requires this extension, otherwise the app crashes
/// with the following message:
/// "UIAlertController:supportedInterfaceOrientations was invoked recursively"
/// Read more at https://stackoverflow.com/a/32010520/10070651.
extension UIAlertController {
  override open var supportedInterfaceOrientations: UIInterfaceOrientationMask {
    // By having the alert supporting only the current orientation, we make sure
    // that we don't override the parent view controller supported orientations.
    // This is fine for users too since they were already in this orientation.
    return currentOrientation().toMask()
  }

  open override var shouldAutorotate: Bool {
    return false
  }
}

Besides

import UIKit

The two line change below should be made so there is no compiler warnings. see https://www.avanderlee.com/swift/unknown-default-enums-in-swift/

extension UIInterfaceOrientation {
public var description: String {
switch self {
case .landscapeLeft:
return "landscapeLeft"
case .landscapeRight:
return "landscapeRight"
case .portrait:
return "portrait"
case .portraitUpsideDown:
return "portraitUpsideDown"
case .unknown:
fallthrough // <<< change
@unknown default: // <<< change
return "unknown"
}
}

func toMask() -> UIInterfaceOrientationMask {
return self.isPortrait ? .portrait : .landscape
}
}