Sample CodevisionOSReviewed 2026-07-21View on Apple Developer

Monitoring fit and field of view fidelity

At a glance

Item Summary
Purpose Respond to changes in fit and field of view fidelity on Apple Vision Pro by using the Visual Fidelity API.
App architecture VisualFidelityApp composes WindowGroup + ImmersiveSpace around ContentView; AppModel coordinates ARKit provider updates and maps anchors into RealityKit content.
Main patterns SwiftUI scene composition, SwiftUI–RealityKit bridge, Explicit immersive-space lifecycle, Observable state owner, Provider session boundary, Async update consumer
Project style Code-rich sample with 8 scanned Swift file(s) and 690 Swift line(s); resources and generated assets are excluded from those counts.

Project structure

Source bundle/
└── ARKit-VisualFidelity/
    ├── VisualFidelityApp.swift  # VisualFidelityApp
    ├── Model/
    │   └── AppModel.swift  # AppModel, ImmersiveSpaceState, MonitoringState
    └── Views/
        ├── ConfigurationView.swift  # ConfigurationView
        ├── ContentView.swift  # ContentView
        ├── ImmersiveView.swift  # ImmersiveView
        ├── StatusView.swift  # StatusView
        ├── ToggleMonitoringButton.swift  # ToggleMonitoringButton
        └── ToggleVisualizationButton.swift  # ToggleVisualizationButton

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.

Overall architecture

Reference code

ARKit-VisualFidelity/VisualFidelityApp.swift:11 — the app or executable entry declares the outer scene lifecycle.

struct VisualFidelityApp: 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

Ownership evidence

ARKit-VisualFidelity/VisualFidelityApp.swift:13 — representative stored state or the nearest verified lifecycle anchor.

@main
struct VisualFidelityApp: App {
    // ...
    @State private var appModel = AppModel()
    // ...
}
Owner Object or state Relationship Mutation authority
VisualFidelityApp AppModel as appModel creates and retains Only the declaring scope writes
ContentView AppModel as appModel receives a shared/non-owning reference The upstream owner controls lifetime; this scope may invoke its mutable API
AppModel MonitoringState as monitoringState stores and coordinates Only the declaring scope writes
AppModel ImmersiveSpaceState as immersiveSpaceState stores and coordinates The owning type coordinates writes

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

Type Responsibility Depends on or conforms to
VisualFidelityApp (ARKit-VisualFidelity/VisualFidelityApp.swift:11) Declares app scenes and top-level dependency lifetime. App
ContentView (ARKit-VisualFidelity/Views/ContentView.swift:11) Presents UI and forwards gestures or lifecycle events. View
AppModel (ARKit-VisualFidelity/Model/AppModel.swift:13) Owns observable feature state and domain transitions. Concrete framework collaborators
ConfigurationView (ARKit-VisualFidelity/Views/ConfigurationView.swift:10) Presents UI and forwards gestures or lifecycle events. View
ImmersiveView (ARKit-VisualFidelity/Views/ImmersiveView.swift:12) Presents UI and forwards gestures or lifecycle events. View
StatusView (ARKit-VisualFidelity/Views/StatusView.swift:11) Presents UI and forwards gestures or lifecycle events. View

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

Symbol Access Verified effect Likely rationale
private(set) var monitoringState: MonitoringState = .stopped (ARKit-VisualFidelity/Model/AppModel.swift:45) private(set) The getter keeps its wider visibility, while mutation stays inside the declaring type and its permitted same-file extensions. Inference: Protect a state invariant while allowing observation.
private let logger = Logger(subsystem: "com.example.apple-samplecode.AR... (ARKit-VisualFidelity/Model/AppModel.swift:19) private Use is restricted to the declaration and same-file extensions permitted by Swift. Inference: Hide implementation details and lifecycle-sensitive state.

No reviewed declaration uses fileprivate, public, open; unmodified Swift declarations are internal.

Reference code

ARKit-VisualFidelity/Model/AppModel.swift:45 — representative visibility boundary.

@Observable
final class AppModel {
    // ...
    private(set) var monitoringState: MonitoringState = .stopped
    // ...
}

Logic ownership and placement

Logic Owning type or file Placement rationale
Scene declaration and dependency lifetime VisualFidelityApp The App/entry boundary determines window, volume, and immersive-space lifetime.
Presentation, attachments, and gestures ContentView SwiftUI view code forwards user intent and RealityView lifecycle events.
Shared feature state and commands AppModel A role-named owner prevents sibling views from duplicating transitions.
Tracking authorization and update streams ARKit-VisualFidelity/Model/AppModel.swift:105 Provider lifetime and async updates remain outside render-only view code.

Design patterns

Pattern Source evidence Purpose or tradeoff
SwiftUI scene composition ARKit-VisualFidelity/VisualFidelityApp.swift:11 Keeps windows, volumes, and immersive-space lifecycle visible at the app boundary.
SwiftUI–RealityKit bridge ARKit-VisualFidelity/Views/ImmersiveView.swift:26 Builds and updates a RealityKit entity graph from SwiftUI lifecycle closures.
Explicit immersive-space lifecycle ARKit-VisualFidelity/VisualFidelityApp.swift:24 Makes immersive presentation a scene transition rather than hidden global state.
Observable state owner ARKit-VisualFidelity/Model/AppModel.swift:13 Shares feature state across multiple views without moving framework resources into view values.
Provider session boundary ARKit-VisualFidelity/Model/AppModel.swift:105 Owns provider lifetime separately from the SwiftUI view tree.
Async update consumer ARKit-VisualFidelity/Model/AppModel.swift:133 Consumes provider or event streams in cancellable structured tasks.

Naming conventions

  • Role suffixes are evidence, not decoration: App: VisualFidelityApp; Model: AppModel; View: ConfigurationView, ContentView, ImmersiveView, StatusView.
  • Protocols: no app-defined protocol in the reviewed source.
  • Commands use verb-led methods: startMonitoring, stopMonitoring, monitor, apply, setAnchor, sync.
  • Files generally match their primary type; Views, Models, Managers, Providers, Components, Systems, and Packages folders describe architectural roles where present.

Architecture takeaways

  • Treat VisualFidelityApp 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.
  • Model immersive-space open, transition, and close states explicitly so windows and immersive content cannot drift apart.

Source map

Source file Relevant symbols
ARKit-VisualFidelity/VisualFidelityApp.swift:11 VisualFidelityApp
ARKit-VisualFidelity/Model/AppModel.swift:13 AppModel, ImmersiveSpaceState, MonitoringState, FieldOfViewSelection
ARKit-VisualFidelity/Views/ConfigurationView.swift:10 ConfigurationView
ARKit-VisualFidelity/Views/ContentView.swift:11 ContentView
ARKit-VisualFidelity/Views/ImmersiveView.swift:12 ImmersiveView
ARKit-VisualFidelity/Views/StatusView.swift:11 StatusView
ARKit-VisualFidelity/Views/ToggleMonitoringButton.swift:10 ToggleMonitoringButton
ARKit-VisualFidelity/Views/ToggleVisualizationButton.swift:10 ToggleVisualizationButton