Simulating physics with collisions in your visionOS app

At a glance

Project structure

Source bundle/
├── PhysicsBodies/
│   ├── PhysicsBodiesApp.swift
│   ├── MainView.swift
│   ├── SphereAttractionComponent.swift
│   ├── SphereAttractionSystem.swift
│   ├── EntityDragGesture.swift
│   ├── ContainmentCollisionBox.swift
│   ├── ForceDragGesture.swift
│   ├── RelocateDragGesture.swift
│   ├── Entity+CollisionPhysicsBox.swift
│   └── Entity+Sphere.swift
├── Configuration/
│   └── SampleCode.xcconfig
└── PhysicsBodies.xcodeproj/
    └── .xcodesamplecode.plist

Structure observations

• Architecturally prominent files are ranked from entry points and role-named declarations; resource-only paths are omitted.
• Primary languages: Swift.
• The verified tree contains 4 project/configuration file(s) and 9 source declaration(s).

Overall architecture

flowchart LR
    N1["PhysicsBodiesApp"]
    N2["MainView"]
    N3["SphereAttractionSystem"]
    N4["RealityKit APIs"]
    N1 --> N2
    N2 --> N3
    N3 --> N4

Reference code

PhysicsBodies/PhysicsBodiesApp.swift:10 — architecture anchor

@main
struct PhysicsBodiesApp: App {
    var body: some Scene {
        WindowGroup {
            MainView()
        }.windowStyle(.volumetric)
    }
}

Interpretation

The arrows summarize the source-visible entry, role-named types or folders, and framework direction; when nodes come from structural folders, the sequence is a high-level interpretation rather than proof that every adjacent node calls the next. Ownership is claimed only where the next section cites a stored property or assignment. The diagram is intentionally limited to the dominant path into RealityKit.

Ownership and state

classDiagram
    MainView *-- ContainmentCollisionBox : containmentCollisionBox
    SphereAttractionSystem o-- EntityQuery : entityQuery
    GestureStateComponent *-- SIMD3 : startPosition
    GestureStateComponent o-- Closure : closure

Ownership evidence

PhysicsBodies/MainView.swift:13 — stored dependency or nearest verified ownership anchor

struct MainView: View {
    // ...
    @State var containmentCollisionBox = ContainmentCollisionBox()
    // ...
}

Composition arrows indicate a source-visible construction expression or locally owned value state; aggregation means the owner stores or receives a dependency without proving exclusive lifetime ownership.

Concurrency, scheduling, and thread safety

Evidence limit: actor isolation, async/await, or Task creation does not by itself prove background-thread execution; Sendable conformance alone does not prove thread-safe mutation.

No source-visible execution, scheduling, or synchronization boundary was found in the indexed source.

@MainActor/MainActor.run, DispatchQueue.main, and RunLoop.main are reported as distinct isolation, queue, and event-loop mechanisms. A plain Task is kept separate from Task.detached; neither is labeled as a background thread.

State propagation, frameworks, and dependencies

Evidence limit: an import proves a source-level compilation dependency at the cited line; it does not prove runtime use, architectural adoption, or whether a Swift package is a direct application dependency.

receive(on:) describes downstream delivery scheduling, while subscribe(on:) describes upstream subscription/request/cancel scheduling. An import Combine alone establishes neither behavior nor a Store, reducer, Redux, or other application architecture.

Class and protocol design

PhysicsBodies/PhysicsBodiesApp.swift:11 — representative type boundary

@main
struct PhysicsBodiesApp: App {
    // ...
            MainView()
    // ...
}

No local protocol conformance is claimed as protocol-oriented design; external framework conformances are listed only as dependencies.

Access control

Reference code

PhysicsBodies/Entity+CollisionPhysicsBox.swift:12 — representative boundary

private let defaultMass1Kg = Float(1.0)

Swift declarations without a modifier are internal; explicit private, fileprivate, private(set), public, or open entries above are interpreted by language semantics. Objective-C/C samples instead rely on header and implementation boundaries, which are not equivalent to Swift lexical privacy.

Logic ownership and placement

Design patterns

Naming conventions

• Types: App: PhysicsBodiesApp; Component: GestureStateComponent, SphereAttractionComponent; System: SphereAttractionSystem; View: MainView.
• Protocols: no local protocol declaration in the scanned source.
• Methods: addSpheres, update, startPosition.
• Files: PhysicsBodies/PhysicsBodiesApp.swift, PhysicsBodies/MainView.swift, PhysicsBodies/SphereAttractionComponent.swift, PhysicsBodies/SphereAttractionSystem.swift, PhysicsBodies/EntityDragGesture.swift, PhysicsBodies/ContainmentCollisionBox.swift.

Architecture takeaways

• PhysicsBodiesApp is the main source-visible entry or composition anchor for this sample.
• Framework work reaches RealityKit, SwiftUI, CoreGraphics, simd through a deliberately small high-level chain; the detailed API graph remains inside the cited implementation files.
• Stored-property evidence identifies lifecycle collaboration; it does not by itself prove exclusive object ownership.
• Access-control conclusions separate verified language visibility from the likely design rationale.
• The source does not justify labeling the design protocol-oriented.

Source map

• Official Apple documentation