Displaying a 3D environment through a portal

At a glance

Project structure

Source bundle/
└── RealityKit-UIPortal/
    └── RealityKit-UIPortal/
        ├── App/
        │   ├── EntryPoint.swift  # EntryPoint
        │   └── AppModel.swift  # AppModel, ImmersiveSpaceState
        ├── Views/
        │   ├── UIPortalView.swift  # UIPortalView
        │   ├── ImmersiveView.swift  # ImmersiveView
        │   └── ToggleImmersiveSpace.swift  # ToggleImmersiveSpaceButton
        └── Extensions/
            └── EnvironmentResource.swift

Structure observations

• The runtime boundary is WindowGroup + ImmersiveSpace; the pruned tree lists only files that explain lifecycle, state, or framework integration.
• App code is compact; any explicit model, provider, or entity owner is still shown below rather than collapsed into view-local state.

Overall architecture

flowchart LR
    EntryPoint_1["EntryPoint"]
    WindowGroup___ImmersiveSpace_2["WindowGroup + ImmersiveSpace"]
    UIPortalView_3["UIPortalView"]
    AppModel_4["AppModel"]
    RealityView_entity_graph_5["RealityView entity graph"]
    RealityKit_entity_graph_6["RealityKit entity graph"]
    EntryPoint_1 --> WindowGroup___ImmersiveSpace_2
    WindowGroup___ImmersiveSpace_2 --> UIPortalView_3
    UIPortalView_3 --> AppModel_4
    AppModel_4 --> RealityView_entity_graph_5
    RealityView_entity_graph_5 --> RealityKit_entity_graph_6

Reference code

RealityKit-UIPortal/RealityKit-UIPortal/App/EntryPoint.swift:11 — the app or executable entry declares the outer scene lifecycle.

struct EntryPoint: 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
    EntryPoint *-- AppModel : appModel
    UIPortalView o-- AppModel : appModel
    UIPortalView *-- Entity : root
    UIPortalView *-- ModelEntity : portalPlane

Ownership evidence

RealityKit-UIPortal/RealityKit-UIPortal/App/EntryPoint.swift:12 — representative stored state or the nearest verified lifecycle anchor.

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

Reference code

RealityKit-UIPortal/RealityKit-UIPortal/App/EntryPoint.swift:12 — representative visibility boundary.

    @State private var appModel = AppModel()

Logic ownership and placement

Design patterns

Naming conventions

• Role suffixes are evidence, not decoration: Model: AppModel; View: ImmersiveView, UIPortalView.
• Protocols: no app-defined protocol in the reviewed source.
• Commands use verb-led methods: createPortal, updatePortalSize, createEnvironment.
• Files generally match their primary type; Views, Models, Managers, Providers, Components, Systems, and Packages folders describe architectural roles where present.

Architecture takeaways

• Treat EntryPoint 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.
• Model immersive-space open, transition, and close states explicitly so windows and immersive content cannot drift apart.
• The compact source does not justify adding repository, coordinator, or protocol layers beyond the model, provider, or view boundary the sample actually declares.

Source map

• Official Apple documentation