Mixing spatial music

At a glance

Project structure

Source bundle/
└── MixingSpatialMusic/
    ├── AppModel.swift  # AppModel, ImmersiveSpaceState
    ├── Views/
    │   ├── ImmersiveView.swift  # ImmersiveView
    │   ├── AudioMixer/
    │   │   └── MixerView.swift  # MixerView
    │   └── SettingsView.swift  # SettingsView
    ├── MixingSpatialMusicApp.swift  # MixingSpatialMusicApp
    ├── ECS/
    │   └── ViewpointComponent.swift  # ViewpointComponent
    └── Model/
        └── AudioStem.swift  # AudioStem, VisualModel

Structure observations

• The runtime boundary is WindowGroup + ImmersiveSpace + SwiftUI/UIKit host; the tree is pruned to lifecycle, state, framework, rendering, and ECS files.
• The source is Swift; role-named types and feature folders separate the major responsibilities.

Overall architecture

flowchart LR
    MixingSpatialMusicApp_1["MixingSpatialMusicApp"]
    WindowGroup___ImmersiveSpace___SwiftUI_UIKit_host_2["WindowGroup + ImmersiveSpace + SwiftUI/UIKit host"]
    ImmersiveView_3["ImmersiveView"]
    AppModel_4["AppModel"]
    RealityKit_entity_graph_5["RealityKit entity graph"]
    RealityKit_spatial_audio_scene_6["RealityKit spatial-audio scene"]
    MixingSpatialMusicApp_1 --> WindowGroup___ImmersiveSpace___SwiftUI_UIKit_host_2
    WindowGroup___ImmersiveSpace___SwiftUI_UIKit_host_2 --> ImmersiveView_3
    ImmersiveView_3 --> AppModel_4
    AppModel_4 --> RealityKit_entity_graph_5
    RealityKit_entity_graph_5 --> RealityKit_spatial_audio_scene_6

Reference code

MixingSpatialMusic/MixingSpatialMusicApp.swift:11 — executable or app-lifecycle anchor.

struct MixingSpatialMusicApp: App {
    // ...
}

The diagram is a responsibility flow, not a claim that every adjacent node directly calls the next. It separates lifecycle, presentation, stable state, framework/session work, and the RealityKit entity graph.

Ownership and state

classDiagram
    MixingSpatialMusicApp *-- AppModel : appModel
    AppModel *-- Entity : root
    AppModel *-- Entity : audioSourcesRoot
    AppModel --> AudioPlaybackGroupController : playbackController

Ownership evidence

MixingSpatialMusic/MixingSpatialMusicApp.swift:13 — representative stored state or nearest verified lifecycle anchor.

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

Ownership is intentionally narrow: environment, bindings, observed objects, weak links, and delegate callbacks do not prove lifetime ownership. Initialized stored services and wrapper-managed state do; entities added inside a RealityKit content closure belong to that entity graph.

Class and protocol design

The reviewed source defines no local substitution protocol. Its App, View, delegate, renderer, ARKit, and RealityKit conformances are framework-facing contracts, so this document does not label the whole app protocol-oriented.

Access control

No reviewed Swift access example uses private(set), public, open; declarations without a modifier are internal.

Reference code

MixingSpatialMusic/AppModel.swift:121 — representative visibility boundary.

    private func makeAudioSource(for stem: AudioStem) -> Entity {
        // Construct an audio source entity for the stem.
        let entity: Entity = .makeAudioSource(for: stem)
        audioSourcesRoot.addChild(entity)
        return entity
    }

Logic ownership and placement

Design patterns

Naming conventions

• Role suffixes are evidence, not decoration: App: MixingSpatialMusicApp; Model: AppModel, VisualModel; Component: ViewpointComponent; View: ImmersiveView, MixerView, SettingsView, TrackView.
• ECS names pair data and behavior: components ViewpointComponent; systems none.
• Protocols: no app-defined protocol in the reviewed source.
• Commands use verb-led methods: teleportToStartingViewpoint, teleport, loadVisualEnvironment, loadAudioEnvironment, loadAudio, addViewpoints, configureAudioMixGroups, makeAudioSource.
• Files and folders use primary-type or responsibility names such as Views, Models, Rendering, Components, Systems, Packages, or feature names where those boundaries exist.

Architecture takeaways

• Treat MixingSpatialMusicApp as the owner of executable or scene lifecycle, not automatically as the owner of every entity created later.
• Keep view/controller input near presentation, but move sessions, reconstruction, capture, rendering, shared game state, or documents into stable owners when their lifetime exceeds one callback or render pass.
• Tie asynchronous session/output consumers to an explicit owner so cancellation and teardown follow the same lifecycle.

Source map

• Official Apple documentation