Streaming an AR experience

At a glance

Project structure

Source bundle/
└── StreamingARFramesLocally/
    ├── AppDelegate.swift
    ├── Renderer/
    │   ├── Renderer.swift
    │   ├── Utilities/
    │   │   ├── BufferView.swift
    │   │   ├── MetalUtils.swift
    │   │   └── RenderDestination.swift
    │   ├── DepthStencilStates.swift
    │   └── PipelineStates.swift
    ├── MultipeerSession.swift
    ├── OverlayViewController.swift
    ├── VideoProcessor.swift
    ├── ViewController.swift
    └── VideoFrameData.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 6 project/configuration file(s) and 19 source declaration(s).

Overall architecture

flowchart LR
    N1["AppDelegate"]
    N2["OverlayViewController"]
    N3["Renderer"]
    N4["ARKit APIs"]
    N1 --> N2
    N2 --> N3
    N3 --> N4

Reference code

StreamingARFramesLocally/AppDelegate.swift:10 — architecture anchor

@main
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
    AppDelegate o-- UIWindow : overlayWindow
    Renderer o-- MTLCommandQueue : commandQueue
    Renderer o-- PipelineStates : pipelineStates

Ownership evidence

StreamingARFramesLocally/AppDelegate.swift:13 — stored dependency or nearest verified ownership anchor

@main
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

StreamingARFramesLocally/OverlayViewController.swift:98 — representative execution boundary

        DispatchQueue.main.async { [self] in
            pipViewWidthConstraint?.constant = width / pipView.contentScaleFactor
            pipViewHeightConstraint?.constant = height / pipView.contentScaleFactor
        }

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

StreamingARFramesLocally/Renderer/Utilities/RenderDestination.swift:13 — representative type boundary

protocol RenderDestination {
    var colorPixelFormat: MTLPixelFormat { get set }
    var depthStencilPixelFormat: MTLPixelFormat { get set }
}

The source explicitly defines local protocol relationships: MTKView → RenderDestination.

Access control

Reference code

StreamingARFramesLocally/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: OverlayViewController, ViewController; Delegate: AppDelegate; Processor: VideoProcessor; Renderer: Renderer; Session: MultipeerSession; View: BufferView.
• Protocols: RenderDestination.
• Methods: application, enqueueFrame, createTexture, mtkView, draw, sendToAllPeers, sendToPeers, session.
• Files: StreamingARFramesLocally/AppDelegate.swift, StreamingARFramesLocally/Renderer/Renderer.swift, StreamingARFramesLocally/MultipeerSession.swift, StreamingARFramesLocally/OverlayViewController.swift, StreamingARFramesLocally/Renderer/Utilities/BufferView.swift, StreamingARFramesLocally/VideoProcessor.swift.

Architecture takeaways

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