Code sharing between iOS and watchOS

Hi CatastropheZero,

1. For the hosting view, use SpriteKit's SwiftUI SpriteView, which renders an SKScene and works on both iOS and watchOS — so you avoid the platform-specific SKView (iOS) vs. WKInterfaceSKScene (watchOS) split.

2. For input, SwiftUI supports the same basic tap/drag gestures on watchOS as on iOS, though you'll often wire them to different in-game actions per platform. There are also inputs unique to watchOS — most notably the Digital Crown via. digitalCrownRotation. To support both cleanly, keep the game logic platform-agnostic and feed it semantic intents rather than raw input. The shared engine never references a touch or the crown — each platform translates its own input into the same intents.

  /// hardware (touches, drags, Digital Crown) onto these cases.
  public enum GameIntent {
      case aim(at: CGPoint)        // a scene-space point (e.g. iOS drag/tap location)
      case moveHorizontal(Double)  // a relative nudge (e.g. watchOS Digital Crown delta)
      case primaryAction           // fire / jump / select — a tap on either platform
  }

  public final class GameScene: SKScene {
      private let player = SKShapeNode(circleOfRadius: 20)
      private var targetX: CGFloat?

      public override func didMove(to view: SKView) { ... }

      /// The ONE entry point for input. Platforms call this; the scene never
      /// touches UIResponder, gestures, or the crown directly.
      public func apply(_ intent: GameIntent) {
          switch intent {
          case .aim(let p):            targetX = p.x
          case .moveHorizontal(let d): targetX = (targetX ?? player.position.x) + CGFloat(d) * 8
          case .primaryAction:         fire()
          }
      }

      public override func update(_ currentTime: TimeInterval) { ... }

      private func fire() { ... }
  }

===================================================================================

// iOS — touches → intents
  SpriteView(scene: scene)
      .gesture(DragGesture(minimumDistance: 0)
          .onChanged { scene.apply(.aim(at: scene.convertPoint(fromView: $0.location))) }
          .onEnded   { _ in scene.apply(.primaryAction) })

  // watchOS — Digital Crown + tap → the SAME intents
  SpriteView(scene: scene)
      .focusable()
      .digitalCrownRotation($crown)
      .onChange(of: crown) { _, new in scene.apply(.moveHorizontal(new - last)); last = new }
      .onTapGesture { scene.apply(.primaryAction) }

1. For the hosting view, use SpriteKit's SwiftUI SpriteView, which renders an SKScene and works on both iOS and watchOS — so you avoid the platform-specific SKView (iOS) vs. WKInterfaceSKScene (watchOS) split.

2. For input, SwiftUI supports the same basic tap/drag gestures on watchOS as on iOS, though you'll often wire them to different in-game actions per platform. There are also inputs unique to watchOS — most notably the Digital Crown via. digitalCrownRotation. To support both cleanly, keep the game logic platform-agnostic and feed it semantic intents rather than raw input. The shared engine never references a touch or the crown — each platform translates its own input into the same intents.

e.g.

/// The platform-agnostic input vocabulary. Every platform maps its own
  /// hardware (touches, drags, Digital Crown) onto these cases.
  public enum GameIntent {
      case aim(at: CGPoint)        // a scene-space point (e.g. iOS drag/tap location)
      case moveHorizontal(Double)  // a relative nudge (e.g. watchOS Digital Crown delta)
      case primaryAction           // fire / jump / select — a tap on either platform
  }

  public final class GameScene: SKScene {
      private let player = SKShapeNode(circleOfRadius: 20)
      private var targetX: CGFloat?

      public override func didMove(to view: SKView) { ... }

      /// The ONE entry point for input. Platforms call this; the scene never
      /// touches UIResponder, gestures, or the crown directly.
      public func apply(_ intent: GameIntent) {
          switch intent {
          case .aim(let p):            targetX = p.x
          case .moveHorizontal(let d): targetX = (targetX ?? player.position.x) + CGFloat(d) * 8
          case .primaryAction:         fire()
          }
      }

      public override func update(_ currentTime: TimeInterval) { ... }

      private func fire() { ... }
  }

===================================================================================

// iOS — touches → intents
  SpriteView(scene: scene)
      .gesture(DragGesture(minimumDistance: 0)
          .onChanged { scene.apply(.aim(at: scene.convertPoint(fromView: $0.location))) }
          .onEnded   { _ in scene.apply(.primaryAction) })

  // watchOS — Digital Crown + tap → the SAME intents
  SpriteView(scene: scene)
      .focusable()
      .digitalCrownRotation($crown)
      .onChange(of: crown) { _, new in scene.apply(.moveHorizontal(new - last)); last = new }
      .onTapGesture { scene.apply(.primaryAction) }