Designing no-code games with Reality Composer Pro 3

At a glance

Project structure

Source bundle/
├── Squirrel/SquirrelApp.swift  # SquirrelApp
├── Squirrel/ContentView.swift  # ContentView
├── Squirrel/DinnerBubbleView.swift  # TreeTalkAttachmentView, SpeechBubbleShape
├── Squirrel/SquirrelTalkAttachmentView.swift  # SquirrelTalkAttachmentView
├── Squirrel/ContentViewAttachments.swift  # StartButtonAttachment, EndScreenAttachment, OrnamentBar
├── Squirrel/UIPreview.swift
└── Data/RealityFiles/Scenes.reality  # authored RealityKit content

Structure observations

• The runtime boundary is WindowGroup + volumetric window; 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
    SquirrelApp_1["SquirrelApp"]
    WindowGroup___volumetric_window_2["WindowGroup + volumetric window"]
    ContentView_3["ContentView"]
    RealityView_entity_graph_4["RealityView entity graph"]
    RealityKit_Scripting_runtime_5["RealityKit Scripting runtime"]
    SquirrelApp_1 --> WindowGroup___volumetric_window_2
    WindowGroup___volumetric_window_2 --> ContentView_3
    ContentView_3 --> RealityView_entity_graph_4
    RealityView_entity_graph_4 --> RealityKit_Scripting_runtime_5

Reference code

Squirrel/SquirrelApp.swift:19 — the app or executable entry declares the outer scene lifecycle.

struct SquirrelApp: 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
    ContentView *-- Entity : scene
    ContentView *-- Array : cancellables
    SquirrelTalkAttachmentView *-- Bool : isVisible

Ownership evidence

Squirrel/ContentView.swift:16 — representative stored state or the nearest verified lifecycle anchor.

    @State var scene: Entity?
    @State var cancellables: [AnyCancellable] = []
    
    @State var squirrelTalkText: String = "zzz"
    @State var squirrelTalkTimer: Float = 0
    @State var showStartButton: Bool = false
    @State var forceHideSquirrelTalk: Bool = false
    @State var showOrnament: Bool = false

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), public, open; unmodified Swift declarations are internal.

Reference code

Squirrel/SquirrelTalkAttachmentView.swift:18 — representative visibility boundary.

struct SquirrelTalkAttachmentView: View {
    // ...
    @State private var displayedText: String = "zzz"
    @State private var scale: CGFloat = 0
    // ...
}

Logic ownership and placement

Design patterns

Naming conventions

• Role suffixes are evidence, not decoration: App: SquirrelApp; View: ContentView, SquirrelTalkAttachmentView, TreeTalkAttachmentView.
• Protocols: no app-defined protocol in the reviewed source.
• Commands use verb-led methods: sendSceneEvent, jumpToScene, formatPlayTime, scriptingEntity, inset, path, addCorner.
• Files generally match their primary type; Views, Models, Managers, Providers, Components, Systems, and Packages folders describe architectural roles where present.

Architecture takeaways

• Treat SquirrelApp 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.
• Count Reality Composer Pro and Script Graph assets as implementation; the Swift shell alone is not the full architecture.

Source map

• Official Apple documentation