Detecting human body poses in an image

At a glance

Project structure

Source bundle/
└── PoseFinder/
    ├── App/
    │   └── AppDelegate.swift
    ├── UI/
    │   ├── ConfigurationViewController.swift
    │   ├── PopOverModalViewController.swift
    │   ├── PoseImageView.swift
    │   ├── GradientOverlayView.swift
    │   └── ViewController.swift
    ├── Pose/
    │   ├── PoseBuilder.swift
    │   ├── Joint.swift
    │   └── Pose.swift
    ├── Model/
    │   ├── PoseNetOutput.swift
    │   └── PoseNet.swift
    └── Utils/
        └── VideoCapture.swift

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 25 source declaration(s).

Overall architecture

flowchart LR
    N1["AppDelegate"]
    N2["ConfigurationViewController"]
    N3["PopOverPresentationManager"]
    N4["CoreML APIs"]
    N1 --> N2
    N2 --> N3
    N3 --> N4

Reference code

PoseFinder/App/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 Core ML.

Ownership and state

classDiagram
    AppDelegate o-- UIWindow : window
    PopOverPresentationManager o-- UIViewController : presentedViewController
    PopOverPresentationManager o-- UIViewController : presentingViewController
    PopOverPresentationController *-- CGFloat : popOverHeightRatio

Ownership evidence

PoseFinder/App/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

PoseFinder/Model/PoseNet.swift:52 — representative execution boundary

        DispatchQueue.global(qos: .userInitiated).async {
            // ...
            let input = PoseNetInput(image: image, size: self.modelInputSize)
            // ...
        }

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

PoseFinder/UI/ConfigurationViewController.swift:11 — representative type boundary

protocol ConfigurationViewControllerDelegate: AnyObject {
    func configurationViewController(_ viewController: ConfigurationViewController,
                                     didUpdateConfiguration: PoseBuilderConfiguration)

    func configurationViewController(_ viewController: ConfigurationViewController,
                                     didUpdateAlgorithm: Algorithm)
}

The source explicitly defines local protocol relationships: ViewController → ConfigurationViewControllerDelegate, ViewController → VideoCaptureDelegate, ViewController → PoseNetDelegate.

Access control

Reference code

PoseFinder/Model/PoseNet.swift:40 — representative boundary

class PoseNet {
    // ...
    private let poseNetMLModel: MLModel
    // ...
}

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: Builder: PoseBuilder; Controller: ConfigurationViewController, PopOverPresentationController, ViewController; Delegate: AppDelegate, ConfigurationViewControllerDelegate, PoseNetDelegate, VideoCaptureDelegate; Manager: PopOverPresentationManager; View: GradientOverlayView, PoseImageView.
• Protocols: ConfigurationViewControllerDelegate, VideoCaptureDelegate, PoseNetDelegate.
• Methods: configurationViewController, viewDidLoad, closeButtonTapped, algorithmValueChanged, jointConfidenceThresholdValueChanged, poseConfidenceThresholdValueChanged, localJointSearchRadiusValueChanged, matchingJointMinimumDistanceValueChanged.
• Files: PoseFinder/App/AppDelegate.swift, PoseFinder/UI/ConfigurationViewController.swift, PoseFinder/UI/PoseImageView.swift, PoseFinder/Pose/PoseBuilder.swift, PoseFinder/UI/GradientOverlayView.swift, PoseFinder/UI/ViewController.swift.

Architecture takeaways

• AppDelegate is the main source-visible entry or composition anchor for this sample.
• Framework work reaches CoreGraphics, UIKit, AVFoundation, CoreML 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