Object tracking with Reality Composer Pro experiences

At a glance

Project structure

Source bundle/
├── ObjectTrackingExperiencesSample/ObjectTrackingExperiencesSampleApp.swift  # ObjectTrackingExperiencesSampleApp
├── ObjectTrackingExperiencesSample/Game/KeyboardGame.swift  # KeyboardGame, Challenge, Outcome
├── ObjectTrackingExperiencesSample/AppModel.swift  # AppModel, ImmersiveSpaceState
├── ObjectTrackingExperiencesSample/Utils/FadeOutComponent.swift  # FadeOutComponent, FadeOutSystem
├── ObjectTrackingExperiencesSample/Views/ContentView.swift  # ContentView
├── ObjectTrackingExperiencesSample/Views/ImmersiveView.swift  # ImmersiveView
├── ObjectTrackingExperiencesSample/Utils/ObjectTrackingGuide.swift  # ObjectTrackingGuide
├── Packages/RealityKitContent/Sources/RealityKitContent/RealityKitContent.swift
└── Packages/RealityKitContent/Package.realitycomposerpro/PluginData/AF09ED6F-1707-48FD-8720-65B998362C09/ShaderGraphEditorPluginID/ShaderGraphEditorPluginID  # authored RealityKit content

Structure observations

• The runtime boundary is WindowGroup + ImmersiveSpace; the pruned tree lists only files that explain lifecycle, state, or framework integration.
• App code is split into role-named views, models, managers, providers, components, or systems.
• Authored .reality or Reality Composer Pro content is a real implementation boundary; Swift loads or drives it rather than reproducing its entity graph.

Overall architecture

flowchart LR
    ObjectTrackingExperiencesSampleApp_1["ObjectTrackingExperiencesSampleApp"]
    WindowGroup___ImmersiveSpace_2["WindowGroup + ImmersiveSpace"]
    ContentView_3["ContentView"]
    AppModel_4["AppModel"]
    RealityView_entity_graph_5["RealityView entity graph"]
    ARKit_providers___RealityKit_6["ARKit providers + RealityKit"]
    ObjectTrackingExperiencesSampleApp_1 --> WindowGroup___ImmersiveSpace_2
    WindowGroup___ImmersiveSpace_2 --> ContentView_3
    ContentView_3 --> AppModel_4
    AppModel_4 --> RealityView_entity_graph_5
    RealityView_entity_graph_5 --> ARKit_providers___RealityKit_6

Reference code

ObjectTrackingExperiencesSample/ObjectTrackingExperiencesSampleApp.swift:10 — the app or executable entry declares the outer scene lifecycle.

struct ObjectTrackingExperiencesSampleApp: App {
    // ...
}

The diagram is a responsibility flow, not a claim that every adjacent node directly calls the next. It keeps scene ownership, shared state, RealityKit content, and framework-provider work at separate levels.

Ownership and state

classDiagram
    ObjectTrackingExperiencesSampleApp *-- AppModel : appModel
    ContentView o-- AppModel : appModel
    ContentView o-- ScenePhase : scenePhase
    ObjectTrackingGuide *-- ARKitSession : arSession

Ownership evidence

ObjectTrackingExperiencesSample/ObjectTrackingExperiencesSampleApp.swift:12 — representative stored state or the nearest verified lifecycle anchor.

@main
struct ObjectTrackingExperiencesSampleApp: App {
    // ...
    @State private var appModel = AppModel()
    // ...
}

Ownership here is deliberately narrow: @Environment and weak references are shared links, initialized @State or stored services are lifecycle ownership, and a RealityView content closure owns additions to its entity graph without making the SwiftUI view a reference-type owner.

Class and protocol design

The source defines no local substitution protocol in the reviewed boundary. Its protocol use is framework-facing (App, View, RealityKit/ARKit protocols, or platform adapters), so this document does not label the whole app protocol-oriented.

Access control

No reviewed declaration uses fileprivate, private(set), open; unmodified Swift declarations are internal.

Reference code

ObjectTrackingExperiencesSample/ObjectTrackingExperiencesSampleApp.swift:12 — representative visibility boundary.

@main
struct ObjectTrackingExperiencesSampleApp: App {
    // ...
    @State private var appModel = AppModel()
    // ...
}

Logic ownership and placement

Design patterns

Naming conventions

• Role suffixes are evidence, not decoration: App: ObjectTrackingExperiencesSampleApp; Model: AppModel; View: ContentView, ImmersiveView.
• ECS names pair data and behavior: components FadeOutComponent; systems FadeOutSystem.
• Protocols: no app-defined protocol in the reviewed source.
• Commands use verb-led methods: loadChallenges, startGame, respond, encode, update, updateAnimation.
• Files generally match their primary type; Views, Models, Managers, Providers, Components, Systems, and Packages folders describe architectural roles where present.

Architecture takeaways

• Treat ObjectTrackingExperiencesSampleApp as the owner of scene declarations, not as the owner of every RealityKit entity created later.
• Keep view-local interaction in SwiftUI, but move provider sessions, playback resources, shared game state, or transport state into a stable owner when their lifetime exceeds one render pass.
• Run ARKit providers for the scene lifetime and consume their asynchronous updates in cancellable tasks; map anchors to entities at the boundary.
• Use RealityKit components for per-entity data and systems for repeated simulation instead of a monolithic view model.
• Model immersive-space open, transition, and close states explicitly so windows and immersive content cannot drift apart.

Source map

• Official Apple documentation