SwiftUI CoreMotion driven DeviceOrientationObserver

SwiftUI_DeviceOrientationObserver.swift

import CoreMotion
import SwiftUI

public final class DeviceOrientationObserver: ObservableObject {
  public init() {
    manager.startAccelerometerUpdates(to: OperationQueue.main) { [weak self] data, error in
      guard error == nil, let acceleration = data?.acceleration else {
        self?.value = .unknown
        return
      }
      self?.value = deviceOrientation(from: acceleration)
    }
  }

  @Published public var value: UIDeviceOrientation = .unknown

  deinit {
    manager.stopAccelerometerUpdates()
  }

  let manager = CMMotionManager()
}

private func deviceOrientation(from acceleration: CMAcceleration) -> UIDeviceOrientation {
  let z = acceleration.z
  if z <= -0.95 { return .faceUp }
  if z >= 0.95 { return .faceDown }

  switch atan2(acceleration.y, -acceleration.x) {
  case -2.25 ... -0.75: return .portrait
  case -0.75 ... 0.75: return .landscapeRight
  case 0.75 ... 2.25: return .portraitUpsideDown
  default: return .landscapeLeft
  }
}

// MARK: - Example

struct ExampleView: View {
  @StateObject var observer = DeviceOrientationObserver()

  var body: some View {
    Text("Device orientation: \(observer.value.title)")
  }
}

extension UIDeviceOrientation {
  var title: String {
    switch self {
    case .unknown: return "unknown"
    case .portrait: return "portrait"
    case .portraitUpsideDown: return "portraitUpsideDown"
    case .landscapeLeft: return "landscapeLeft"
    case .landscapeRight: return "landscapeRight"
    case .faceUp: return "faceUp"
    case .faceDown: return "faceDown"
    @unknown default: return "unknown default"
    }
  }
}