Tracking accessories in volumetric windows

At a glance

Project structure

Source bundle/
└── TrackingAccessories/
    ├── TrackingAccessoriesApp.swift
    ├── Models/
    │   ├── SpatialController.swift
    │   ├── AccessoryTrackingModel.swift
    │   └── ThrowSpeedTracker.swift
    ├── Views/
    │   ├── AccessoryTrackingView.swift
    │   ├── AppStateView.swift
    │   └── GameStateView.swift
    └── Entities/
        ├── Arrow3D.swift
        ├── Ball.swift
        ├── Can.swift
        ├── CanStack.swift
        └── Crate.swift

Structure observations

• Architecturally prominent files are ranked from entry points and role-named declarations; resource-only paths are omitted.
• Primary languages: Swift.
• The verified tree contains 4 project/configuration file(s) and 18 source declaration(s).

Overall architecture

flowchart LR
    N1["TrackingAccessoriesApp"]
    N2["AccessoryTrackingView"]
    N3["AccessoryTrackingModel"]
    N4["ThrowSpeedTracker"]
    N5["ARKit APIs"]
    N1 --> N2
    N2 --> N3
    N3 --> N4
    N4 --> N5

Reference code

TrackingAccessories/TrackingAccessoriesApp.swift:12 — architecture anchor

@main
struct TrackingAccessoriesApp: App {
    var body: some SwiftUI.Scene {
        WindowGroup {
            AccessoryTrackingView()
        }
        .windowStyle(.volumetric)
    }
}

Interpretation

The arrows summarize the source-visible entry, role-named types or folders, and framework direction; when nodes come from structural folders, the sequence is a high-level interpretation rather than proof that every adjacent node calls the next. Ownership is claimed only where the next section cites a stored property or assignment. The diagram is intentionally limited to the dominant path into ARKit.

Ownership and state

classDiagram
    SpatialController o-- AccessoryAnchor : anchor
    SpatialController *-- Throw : pendingThrow
    SpatialController o-- Throw : triggeredThrow
    SpatialController *-- Shake : pendingShake

Ownership evidence

TrackingAccessories/Models/SpatialController.swift:13 — stored dependency or nearest verified ownership anchor

@Observable
@MainActor
final class SpatialController {
    var anchor: AccessoryAnchor? = nil
    // ...
}

Composition arrows indicate a source-visible construction expression or locally owned value state; aggregation means the owner stores or receives a dependency without proving exclusive lifetime ownership.

Concurrency, scheduling, and thread safety

Evidence limit: actor isolation, async/await, or Task creation does not by itself prove background-thread execution; Sendable conformance alone does not prove thread-safe mutation.

@MainActor/MainActor.run, DispatchQueue.main, and RunLoop.main are reported as distinct isolation, queue, and event-loop mechanisms. A plain Task is kept separate from Task.detached; neither is labeled as a background thread.

Reference code

TrackingAccessories/Entities/Arrow3D.swift:10 — representative execution boundary

@MainActor
class Arrow3D: Entity, HasModel {
    static private let shaftLength: Float = 1.0
    // ...
}

State propagation, frameworks, and dependencies

Evidence limit: an import proves a source-level compilation dependency at the cited line; it does not prove runtime use, architectural adoption, or whether a Swift package is a direct application dependency.

receive(on:) describes downstream delivery scheduling, while subscribe(on:) describes upstream subscription/request/cancel scheduling. An import Combine alone establishes neither behavior nor a Store, reducer, Redux, or other application architecture.

Class and protocol design

TrackingAccessories/TrackingAccessoriesApp.swift:13 — representative type boundary

@main
struct TrackingAccessoriesApp: App {
    // ...
            AccessoryTrackingView()
    // ...
}

No local protocol conformance is claimed as protocol-oriented design; external framework conformances are listed only as dependencies.

Access control

Reference code

TrackingAccessories/Entities/CanStack.swift:10 — representative boundary

private let verticalSpacing: Float = 0.18

Swift declarations without a modifier are internal; explicit private, fileprivate, private(set), public, or open entries above are interpreted by language semantics. Objective-C/C samples instead rely on header and implementation boundaries, which are not equivalent to Swift lexical privacy.

Logic ownership and placement

Design patterns

Main application flow

sequenceDiagram
    participant AccessoryTrackingModel
    participant Task
    participant Accessory
    participant arkitSession
    participant accessoryTracking
    AccessoryTrackingModel->>Task: Start asynchronous work
    AccessoryTrackingModel->>Accessory: Accessory()
    AccessoryTrackingModel->>arkitSession: run()
    accessoryTracking-->>AccessoryTrackingModel: update() stream

Reference code

TrackingAccessories/Models/AccessoryTrackingModel.swift:268 — trackAllConnectedSpatialControllers()

    private func trackAllConnectedSpatialControllers() {
        // ...
        Task {
            guard state != .accessoryTrackingNotAuthorized && state != .accessoryTrackingNotSupported else {
                print("Can't run ARKit session: \(state)")
                return
            }
            var accessories: [Accessory] = []
            for spatialController in GCController.spatialControllers() {
                do {
                    let accessory = try await Accessory(device: spatialController)
                    accessories.append(accessory)
                } catch {
                    print("Error during accessory initialization: \(error)")
                }
            }
            guard !accessories.isEmpty else {
                state = .noControllerConnected
                arkitSession.stop()
                return
            }
            let accessoryTracking = AccessoryTrackingProvider(accessories: accessories)
            do {
                try await arkitSession.run([accessoryTracking])
                state = .inGame
                gameState = .startNewGame
            } catch {
                return
            }
            for await update in accessoryTracking.anchorUpdates {
                process(update)
            }
        }
    }

Naming conventions

• Types: App: TrackingAccessoriesApp; Controller: SpatialController; Model: AccessoryTrackingModel; Tracker: ThrowSpeedTracker; View: AccessoryTrackingView, AppStateView, GameStateView.
• Protocols: no local protocol declaration in the scanned source.
• Methods: ballThrown, setCanIsToppled, stopTracking, controller, actOnThrow, actOnShake, trackAllConnectedSpatialControllers, process.
• Files: TrackingAccessories/TrackingAccessoriesApp.swift, TrackingAccessories/Models/SpatialController.swift, TrackingAccessories/Models/AccessoryTrackingModel.swift, TrackingAccessories/Models/ThrowSpeedTracker.swift, TrackingAccessories/Views/AccessoryTrackingView.swift, TrackingAccessories/Views/AppStateView.swift.

Architecture takeaways

• TrackingAccessoriesApp is the main source-visible entry or composition anchor for this sample.
• Framework work reaches RealityKit, ARKit, SwiftUI, GameController through a deliberately small high-level chain; the detailed API graph remains inside the cited implementation files.
• Stored-property evidence identifies lifecycle collaboration; it does not by itself prove exclusive object ownership.
• Access-control conclusions separate verified language visibility from the likely design rationale.
• The source does not justify labeling the design protocol-oriented.

Source map

• Official Apple documentation