Exploring object tracking with ARKit

At a glance

Project structure

Source bundle/
├── ObjectTracking/
│   ├── ObjectTrackingApp.swift
│   ├── App/
│   │   ├── ObjectAnchorVisualization.swift
│   │   ├── ReferenceObjectLoader.swift
│   │   └── AppState.swift
│   ├── Views/
│   │   ├── HomeView.swift
│   │   ├── ListEntryView.swift
│   │   ├── ObjectTrackingRealityView.swift
│   │   └── InfoLabel.swift
│   └── Extensions/
│       └── Entity+ObjectTracking.swift
├── Configuration/
│   └── SampleCode.xcconfig
└── ObjectTracking.xcodeproj/
    ├── .xcodesamplecode.plist
    └── project.pbxproj

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 13 source declaration(s).

Overall architecture

flowchart LR
    N1["ObjectTrackingApp"]
    N2["HomeView"]
    N3["ReferenceObjectLoader"]
    N4["ARKit / SwiftUI APIs"]
    N1 --> N2
    N2 --> N3
    N3 --> N4

Reference code

ObjectTracking/ObjectTrackingApp.swift:14 — architecture anchor

@main
@MainActor
struct ObjectTrackingApp: App {
    @State private var appState = AppState()

    var body: some Scene {
        WindowGroup {
            HomeView(
                appState: appState,
                immersiveSpaceIdentifier: UIIdentifier.immersiveSpace
            )
            .task {
                if appState.allRequiredProvidersAreSupported {
                    await appState.referenceObjectLoader.loadBuiltInReferenceObjects()
                }
            }
        }
        .windowStyle(.plain)

        ImmersiveSpace(id: UIIdentifier.immersiveSpace) {
            ObjectTrackingRealityView(appState: appState)
        }
    }
}

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 visionOS.

Ownership and state

classDiagram
    ObjectTrackingApp *-- AppState : appState
    ObjectAnchorVisualization *-- Float : textBaseHeight
    ObjectAnchorVisualization *-- CGFloat : alpha
    ObjectAnchorVisualization *-- Float : axisScale

Ownership evidence

ObjectTracking/ObjectTrackingApp.swift:17 — stored dependency or nearest verified ownership anchor

@main
@MainActor
struct ObjectTrackingApp: App {
    @State private var appState = AppState()
    // ...
}

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

ObjectTracking/App/AppState.swift:10 — representative execution boundary

@MainActor
@Observable
final class AppState {
    var isImmersiveSpaceOpened = false
    // ...
}

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

ObjectTracking/ObjectTrackingApp.swift:16 — representative type boundary

@main
@MainActor
struct ObjectTrackingApp: App {
    @State private var appState = AppState()
    // ...
}

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

Access control

Reference code

ObjectTracking/App/AppState.swift:32 — representative boundary

@MainActor
@Observable
final class AppState {
    // ...
    private let arkitSession = ARKitSession()
    // ...
}

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

Naming conventions

• Types: App: ObjectTrackingApp; Loader: ReferenceObjectLoader; View: HomeView, ListEntryView, MetricCoordinateLabelView, ObjectTrackingRealityView.
• Protocols: no local protocol declaration in the scanned source.
• Methods: update, labelText, finishedOneFile, updateProgress, loadBuiltInReferenceObjects, loadReferenceObject, addReferenceObject, removeObject.
• Files: ObjectTracking/ObjectTrackingApp.swift, ObjectTracking/App/ObjectAnchorVisualization.swift, ObjectTracking/App/ReferenceObjectLoader.swift, ObjectTracking/Views/HomeView.swift, ObjectTracking/Views/ListEntryView.swift, ObjectTracking/Views/ObjectTrackingRealityView.swift.

Architecture takeaways

• ObjectTrackingApp is the main source-visible entry or composition anchor for this sample.
• Framework work reaches ARKit, SwiftUI, RealityKit, UIKit 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