Building an immersive experience with RealityKit

At a glance

Project structure

Source bundle/
└── BugBreakAR/
    ├── Components/
    │   ├── EntitySwitcherComponent.swift
    │   ├── InteractionComponent.swift
    │   ├── PathfindingComponent.swift
    │   ├── AudioComponent.swift
    │   ├── VoxelTrailComponent.swift
    │   └── CustomCameraComponent.swift
    ├── AppDelegate.swift
    ├── DebugSettings/
    │   ├── DebugSettings.swift
    │   ├── DebugSettingsCell.swift
    │   └── DebugSettingsViewController.swift
    ├── GameManager.swift
    └── GameViewController.swift

Structure observations

• Architecturally prominent files are ranked from entry points and role-named declarations; resource-only paths are omitted.
• Primary languages: C/Objective-C header, Metal, Swift.
• The verified tree contains 8 project/configuration file(s) and 83 source declaration(s).

Overall architecture

flowchart LR
    N1["AppDelegate"]
    N2["DebugSettingsViewController"]
    N3["GameManager"]
    N4["MetalRenderer"]
    N5["RealityKit APIs"]
    N1 --> N2
    N2 --> N3
    N3 --> N4
    N4 --> N5

Reference code

BugBreakAR/AppDelegate.swift:12 — architecture anchor

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {
    var window: UIWindow?
    // ...
}

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
    EntitySwitcherComponent *-- OSLog : log
    ChildEntityInfo *-- String : name
    ChildEntityInfo o-- EntitySwitcherAnimationType : type
    ChildEntityInfo o-- Scene : scene

Ownership evidence

BugBreakAR/Components/EntitySwitcherComponent.swift:15 — stored dependency or nearest verified ownership anchor

private let log = OSLog(subsystem: appSubsystem, category: "EntitySwitchComponent")

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.

@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.

Reference code

BugBreakAR/CreatureEntity.swift:390 — representative execution boundary

            resetPhysics()
            physicsBody?.mode = .kinematic
            DispatchQueue.main.async {
                guard let shatterModel = self.gameManager?.assets?.shatterVoxels else { return }
                // ...
            }

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

BugBreakAR/Components/EntitySwitcherComponent.swift:68 — representative type boundary

public protocol EntitySwitcherComponentDelegate: AnyObject {
    func animationCompleted()
}

The source explicitly defines local protocol relationships: DebugSettingBool → DebugSettingProtocol, DebugSettingInt → DebugSettingProtocol, DebugSettingFloat → DebugSettingProtocol, DebugSettingEnum → DebugSettingProtocol, CreatureEntity → HasEntitySwitcher, CreatureEntity → EntitySwitcherComponentDelegate.

Access control

Reference code

BugBreakAR/Classifications.swift:11 — representative boundary

class Classifications {
    public static var isUpdating: Bool = false
    // ...
}

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: Component: AudioComponent, CustomCameraComponent, EntitySwitcherComponent, HasAudioComponent, InteractionComponent; Controller: DebugSettingsViewController, GameViewController, MainMenuViewController; Delegate: AppDelegate, EntitySwitcherComponentDelegate, GameViewControllerDelegate, InputSystemDelegate, InteractionComponentDelegate; Manager: GameManager; Model: MetalModel; Player: PathfindingBehaviorTurnAwayFromPlayer; Renderer: MetalRenderer; System: InputSystem.
• Protocols: EntitySwitcherComponentDelegate, InteractionComponentDelegate, PathfindingComponentDelegate, HasAudioComponent, GameViewControllerDelegate, InputSystemDelegate, OptionsSettingsDelegate, HasEntitySwitcher.
• Methods: animationCompleted, addChildEntity, fixChild, didClone, forEach, registerCompletion, activateEntity, deactivateEntity.
• Files: BugBreakAR/Components/EntitySwitcherComponent.swift, BugBreakAR/AppDelegate.swift, BugBreakAR/Components/InteractionComponent.swift, BugBreakAR/Components/PathfindingComponent.swift, BugBreakAR/DebugSettings/DebugSettings.swift, BugBreakAR/Components/AudioComponent.swift.

Architecture takeaways

• AppDelegate is the main source-visible entry or composition anchor for this sample.
• Framework work reaches RealityKit, ARKit, UIKit, MetalKit 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.
• Local protocol relationships provide an explicit substitution boundary.

Source map

• Official Apple documentation