Transforming RealityKit entities using gestures

At a glance

Project structure

Source bundle/
├── Packages/RealityKitContent/Sources/RealityKitContent/Components/GestureComponent.swift  # EntityGestureState, GestureComponent
├── EntityGestures/ContentView.swift  # ContentView
├── EntityGestures/EntityGestureApp.swift  # EntityGestureApp
├── Packages/RealityKitContent/Sources/RealityKitContent/Extensions/EntityExtensions.swift
├── Packages/RealityKitContent/Sources/RealityKitContent/Extensions/GestureExtensions.swift
├── Packages/RealityKitContent/Sources/RealityKitContent/Extensions/RealityViewExtensions.swift
├── Packages/RealityKitContent/Sources/RealityKitContent/RealityKitContent.swift
└── Packages/RealityKitContent/Package.realitycomposerpro/ProjectData/main.json  # authored RealityKit content

Structure observations

• The runtime boundary is WindowGroup + volumetric window; 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.
• Authored .reality, .rkassets, or Reality Composer Pro content is an implementation boundary; Swift loads or drives it rather than reproducing its entity graph.

Overall architecture

flowchart LR
    EntityGestureApp_1["EntityGestureApp"]
    WindowGroup___volumetric_window_2["WindowGroup + volumetric window"]
    ContentView_3["ContentView"]
    GestureComponent_4["GestureComponent"]
    RealityKit_entity_graph_5["RealityKit entity graph"]
    targeted_gestures___entity_state_6["targeted gestures + entity state"]
    EntityGestureApp_1 --> WindowGroup___volumetric_window_2
    WindowGroup___volumetric_window_2 --> ContentView_3
    ContentView_3 --> GestureComponent_4
    GestureComponent_4 --> RealityKit_entity_graph_5
    RealityKit_entity_graph_5 --> targeted_gestures___entity_state_6

Reference code

EntityGestures/EntityGestureApp.swift:12 — executable or app-lifecycle anchor.

struct EntityGestureApp: 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
    GestureComponent *-- Entity : pivotEntity
    EntityGestureState --> Entity : targetedEntity
    EntityGestureState --> Entity : pivotEntity
    GestureComponent *-- Transform : targetPivotTransform

Ownership evidence

Packages/RealityKitContent/Sources/RealityKitContent/Components/GestureComponent.swift:120 — representative stored state or nearest verified lifecycle anchor.

@MainActor
public struct GestureComponent: Component, Codable {
    // ...
            let pivotEntity = Entity()
    // ...
}

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 fileprivate, private(set), open; declarations without a modifier are internal.

Reference code

Packages/RealityKitContent/Sources/RealityKitContent/Components/GestureComponent.swift:58 — representative visibility boundary.

@MainActor
public struct GestureComponent: Component, Codable {
    // ...
    public var canDrag: Bool = true
    // ...
}

Logic ownership and placement

Design patterns

Naming conventions

• Role suffixes are evidence, not decoration: App: EntityGestureApp; Component: GestureComponent; View: ContentView.
• ECS names pair data and behavior: components GestureComponent; systems none.
• Protocols: no app-defined protocol in the reviewed source.
• Commands use verb-led methods: onChanged, handlePivotDrag, handleFixedDrag, onEnded, useGestureComponent, installGestures.
• 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 EntityGestureApp 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.
• Count authored Reality Composer Pro assets as implementation; the Swift shell is not the complete architecture.

Source map

• Official Apple documentation