Detecting animal body poses with Vision

At a glance

Project structure

Source bundle/
├── AnimalPoseDetection/
│   ├── AnimalPoseDetectionApp.swift
│   ├── AnimalSkeletonView.swift
│   ├── CameraViewController.swift
│   ├── AnimalEmojiView.swift
│   ├── CameraView.swift
│   ├── ContentView.swift
│   └── AnimalPoseDetector.swift
├── AnimalPoseDetection.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 3 project/configuration file(s) and 9 source declaration(s).

Overall architecture

flowchart LR
    N1["AnimalPoseDetectionApp"]
    N2["ContentView"]
    N3["Vision APIs"]
    N1 --> N2
    N2 --> N3

Reference code

AnimalPoseDetection/AnimalPoseDetectionApp.swift:10 — architecture anchor

@main
struct AnimalPoseDetectionApp: App {
    var body: some Scene {
        WindowGroup {
            ContentView()
        }
    }
}

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 Vision.

Ownership and state

classDiagram
    AnimalSkeletonView *-- AnimalPoseDetector : animalJoint
    AnimalSkeletonView *-- CGSize : size
    Line *-- Array : points
    Line *-- CGSize : size

Ownership evidence

AnimalPoseDetection/AnimalSkeletonView.swift:12 — stored dependency or nearest verified ownership anchor

struct AnimalSkeletonView: View {
    // ...
    @StateObject var animalJoint = AnimalPoseDetector()
    // ...
}

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

AnimalPoseDetection/CameraViewController.swift:35 — representative execution boundary

            DispatchQueue.global(qos: .background).async {
                self.cameraSession?.startRunning()
            }

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

AnimalPoseDetection/AnimalPoseDetectionApp.swift:11 — representative type boundary

@main
struct AnimalPoseDetectionApp: App {
    // ...
            ContentView()
    // ...
}

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

Access control

Reference code

AnimalPoseDetection/CameraViewController.swift:14 — representative boundary

final class CameraViewController: UIViewController {
    private var cameraSession: AVCaptureSession?
    // ...
}

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: AnimalPoseDetectionApp; Controller: CameraViewController; View: AnimalEmojiView, AnimalSkeletonView, CameraView, ContentView, DisplayView.
• Protocols: no local protocol declaration in the scanned source.
• Methods: path, loadView, viewDidAppear, viewWillDisappear, prepareAVSession, makeUIViewController, updateUIViewController, captureOutput.
• Files: AnimalPoseDetection/AnimalPoseDetectionApp.swift, AnimalPoseDetection/AnimalSkeletonView.swift, AnimalPoseDetection/CameraViewController.swift, AnimalPoseDetection/AnimalEmojiView.swift, AnimalPoseDetection/CameraView.swift, AnimalPoseDetection/ContentView.swift.

Architecture takeaways

• AnimalPoseDetectionApp is the main source-visible entry or composition anchor for this sample.
• Framework work reaches SwiftUI, AVFoundation, UIKit, Vision 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