SwiftUI view modifier that performs action whenever UIInterfaceOrientation reported by UIViewController changes

SwiftUI_InterfaceOrientationObservingViewModifier.swift

import SwiftUI

struct InterfaceOrientationObservingViewModifier: ViewModifier {
  let onChange: (UIInterfaceOrientation) -> Void

  func body(content: Content) -> some View {
    content.background(InterfaceOrientationObservingView(onChange: onChange))
  }
}

extension View {
  func onInterfaceOrientationChange(perform: @escaping (UIInterfaceOrientation) -> Void) -> some View {
    modifier(InterfaceOrientationObservingViewModifier(onChange: perform))
  }
}

private struct InterfaceOrientationObservingView: UIViewControllerRepresentable {
  let onChange: (UIInterfaceOrientation) -> Void

  func makeUIViewController(context: Context) -> InterfaceOrientationObservingViewController {
    InterfaceOrientationObservingViewController(onChange: onChange)
  }

  func updateUIViewController(_ uiViewController: InterfaceOrientationObservingViewController, context: Context) {}
}

private final class InterfaceOrientationObservingViewController: UIViewController {
  init(onChange: @escaping (UIInterfaceOrientation) -> Void) {
    self.onChange = onChange
    super.init(nibName: nil, bundle: nil)
  }

  required init?(coder: NSCoder) { nil }

  let onChange: (UIInterfaceOrientation) -> Void
  var lastOrientation: UIInterfaceOrientation?

  override func viewWillTransition(to size: CGSize, with coordinator: UIViewControllerTransitionCoordinator) {
    super.viewWillTransition(to: size, with: coordinator)
    perform()
  }

  override func willTransition(to newCollection: UITraitCollection, with coordinator: UIViewControllerTransitionCoordinator) {
    super.willTransition(to: newCollection, with: coordinator)
    perform()
  }

  override func viewDidAppear(_ animated: Bool) {
    super.viewDidAppear(animated)
    perform()
  }

  func perform() {
    guard let orientation = view.window?.windowScene?.interfaceOrientation else { return }
    guard lastOrientation == nil || lastOrientation != orientation else { return }
    lastOrientation = orientation
    onChange(orientation)
  }
}