Counting human body action repetitions in a live video feed

At a glance

Project structure

Source bundle/
├── CountMyActions/
│   ├── App/
│   │   ├── MyApp.swift
│   │   └── ContentView.swift
│   ├── Model/
│   │   └── ViewModel.swift
│   ├── Views/
│   │   ├── CameraView.swift
│   │   ├── CameraWithPosesAndOverlaysView.swift
│   │   ├── OverlayView.swift
│   │   └── PosesView.swift
│   ├── CountingPipeline/
│   │   └── ActionCounter.swift
│   └── DrawPose/
│       ├── Connection.swift
│       ├── Joint.swift
│       └── Pose.swift
└── 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 5 project/configuration file(s) and 9 source declaration(s).

Overall architecture

flowchart LR
    N1["MyApp"]
    N2["ContentView"]
    N3["ViewModel"]
    N4["CreateMLComponents APIs"]
    N1 --> N2
    N2 --> N3
    N3 --> N4

Reference code

CountMyActions/App/MyApp.swift:10 — architecture anchor

@main
struct MyApp: 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 Create ML Components.

Ownership and state

classDiagram
    ViewModel o-- Pose : liveCameraImageAndPoses
    ViewModel *-- Float : uiCount
    ViewModel o-- Task : displayCameraTask
    ViewModel o-- Task : predictionTask

Ownership evidence

CountMyActions/Model/ViewModel.swift:15 — stored dependency or nearest verified ownership anchor

class ViewModel: ObservableObject {
    // ...
    @Published var liveCameraImageAndPoses: (image: CGImage, poses: [Pose])?
    // ...
}

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

CountMyActions/CountingPipeline/ActionCounter.swift:36 — representative execution boundary

    func count(_ poseStream: AnyTemporalSequence<[Pose]>) async throws -> HumanBodyActionCounter.CumulativeSumSequence {
        return try await pipeline(poseStream)
    }

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

CountMyActions/App/MyApp.swift:11 — representative type boundary

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

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

Access control

Reference code

CountMyActions/DrawPose/Connection.swift:27 — representative boundary

    struct Connection: Equatable {
        // ...
        private let point1: CGPoint
        // ...
    }

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

Main application flow

sequenceDiagram
    participant ViewModel
    participant VideoReader
    participant poseExtractor
    participant poseStream
    ViewModel->>VideoReader: readCamera()
    ViewModel-->>ViewModel: frame() stream
    ViewModel->>poseExtractor: applied()
    ViewModel->>poseStream: send()
    ViewModel->>ViewModel: display()

Reference code

CountMyActions/Model/ViewModel.swift:107 — displayPoseInCamera()

    func displayPoseInCamera() async throws {
        // Start reading the camera.
        let frameSequence = try await VideoReader.readCamera(
            configuration: configuration
        )
        var lastTime = CFAbsoluteTimeGetCurrent()

        for try await frame in frameSequence {

            if Task.isCancelled {
                return
            }

            // Extract poses in every frame.
            let poses = try await poseExtractor.applied(to: frame.feature)

            // Send poses into another pose stream for additional consumers.
            await poseStream.send(TemporalFeature(id: frame.id, feature: poses))

            // Calculate poses from the image frame and display both.
            if let cgImage = CIContext()
                .createCGImage(frame.feature, from: frame.feature.extent) {
                await display(image: cgImage, poses: poses)
            }

            // Frame rate debug information.
            print(String(format: "Frame rate %2.2f fps", 1 / (CFAbsoluteTimeGetCurrent() - lastTime)))
            lastTime = CFAbsoluteTimeGetCurrent()
        }
    }

Naming conventions

• Types: App: MyApp; View: CameraView, CameraWithPosesAndOverlaysView, ContentView, OverlayView, PosesView; ViewModel: ViewModel.
• Protocols: no local protocol declaration in the scanned source.
• Methods: initialize, onCameraButtonTapped, toggleCameraSelection, startVideoProcessingPipeline, displayPoseInCamera, predictCount, display, bubbleBackground.
• Files: CountMyActions/App/MyApp.swift, CountMyActions/Model/ViewModel.swift, CountMyActions/Views/CameraView.swift, CountMyActions/Views/CameraWithPosesAndOverlaysView.swift, CountMyActions/Views/OverlayView.swift, CountMyActions/Views/PosesView.swift.

Architecture takeaways

• MyApp is the main source-visible entry or composition anchor for this sample.
• Framework work reaches SwiftUI, CreateMLComponents, AsyncAlgorithms 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