Creating a multiuser AR experience

At a glance

Project structure

Source bundle/
├── ARMultiuser/
│   ├── AppDelegate.swift
│   ├── MultipeerSession.swift
│   ├── ViewController.swift
│   ├── RoundedButton.swift
│   ├── Utilities.swift
│   ├── Base.lproj/
│   │   ├── LaunchScreen.storyboard
│   │   └── Main.storyboard
│   └── Info.plist
├── ARMultiuser.xcodeproj/
│   ├── .xcodesamplecode.plist
│   └── project.pbxproj
└── Configuration/
    └── SampleCode.xcconfig

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 6 project/configuration file(s) and 4 source declaration(s).

Overall architecture

flowchart LR
    N1["AppDelegate"]
    N2["ViewController"]
    N3["MultipeerSession"]
    N4["ARKit APIs"]
    N1 --> N2
    N2 --> N3
    N3 --> N4

Reference code

ARMultiuser/AppDelegate.swift:10 — 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 ARKit.

Ownership and state

classDiagram
    AppDelegate o-- UIWindow : window
    MultipeerSession *-- MCPeerID : myPeerID
    MultipeerSession o-- MCSession : session
    MultipeerSession o-- MCNearbyServiceAdvertiser : serviceAdvertiser

Ownership evidence

ARMultiuser/AppDelegate.swift:12 — stored dependency or nearest verified ownership anchor

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

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

ARMultiuser/ViewController.swift:124 — representative execution boundary

        DispatchQueue.main.async {
            // ...
            let alertController = UIAlertController(title: "The AR session failed.", message: errorMessage, preferredStyle: .alert)
            // ...
        }

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

ARMultiuser/AppDelegate.swift:11 — representative type boundary

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

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

Access control

Reference code

ARMultiuser/MultipeerSession.swift:13 — representative boundary

class MultipeerSession: NSObject {
    // ...
    private let myPeerID = MCPeerID(displayName: UIDevice.current.name)
    // ...
}

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: Controller: ViewController; Delegate: AppDelegate; Session: MultipeerSession.
• Protocols: no local protocol declaration in the scanned source.
• Methods: sendToAllPeers, session, browser, advertiser, viewDidLoad, viewDidAppear, viewWillDisappear, renderer.
• Files: ARMultiuser/AppDelegate.swift, ARMultiuser/MultipeerSession.swift, ARMultiuser/ViewController.swift, ARMultiuser/RoundedButton.swift.

Architecture takeaways

• AppDelegate is the main source-visible entry or composition anchor for this sample.
• Framework work reaches UIKit, ARKit, MultipeerConnectivity, SceneKit 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