Controlling a DockKit accessory using your camera app

At a glance

Project structure

Source bundle/
└── DockKitCamera/
    ├── DockKit_CameraApp.swift
    ├── Model/
    │   ├── DataTypes.swift
    │   ├── CameraModel.swift
    │   ├── DockAccessoryController.swift
    │   └── DockControllerModel.swift
    ├── Preview Content/
    │   ├── PreviewCameraModel.swift
    │   └── PreviewDockAccessoryControllerModel.swift
    ├── Views/
    │   ├── CameraPreview.swift
    │   └── BatteryView.swift
    ├── CaptureService.swift
    ├── ContentView.swift
    └── DockControlService.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 4 project/configuration file(s) and 58 source declaration(s).

Overall architecture

flowchart LR
    N1["DockKit_CameraApp"]
    N2["ContentView"]
    N3["CameraModel"]
    N4["CaptureService"]
    N5["DockKit APIs"]
    N1 --> N2
    N2 --> N3
    N3 --> N4
    N4 --> N5

Reference code

DockKitCamera/DockKit_CameraApp.swift:11 — architecture anchor

@main
struct DockKitCameraApp: App {
    // ...
}

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 DockKit.

Ownership and state

classDiagram
    DockKitCameraApp *-- CameraModel : camera
    DockKitCameraApp *-- DockControllerModel : dockController
    DockKitCameraApp *-- Logger : logger
    Movie *-- URL : url

Ownership evidence

DockKitCamera/DockKit_CameraApp.swift:14 — stored dependency or nearest verified ownership anchor

@main
struct DockKitCameraApp: App {
    // ...
    @State private var camera = CameraModel()
    // ...
}

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.

Class and protocol design

DockKitCamera/Model/DataTypes.swift:113 — representative type boundary

protocol OutputService {
    associatedtype Output: AVCaptureOutput
    var output: Output { get }
    var captureActivity: CaptureActivity { get }
    func updateConfiguration(for device: AVCaptureDevice)
    func setVideoRotationAngle(_ angle: CGFloat)
}

The source explicitly defines local protocol relationships: MovieCapture → OutputService, CameraModel → Camera, DockControllerModel → DockController, PreviewCameraModel → Camera, PreviewSourceStub → PreviewSource, PreviewDockControllerModel → DockController.

Access control

Reference code

DockKitCamera/Camera/DeviceLookup.swift:15 — representative boundary

final class DeviceLookup {
    // ...
    private let frontCameraDiscoverySession: AVCaptureDevice.DiscoverySession
    // ...
}

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: DockKitCameraApp; Controller: DockController; Delegate: CameraCaptureDelegate, DockAccessoryTrackingDelegate, MovieCaptureDelegate; Model: CameraModel, DockControllerModel, PreviewCameraModel, PreviewDockControllerModel; Service: CaptureService, DockControlService, OutputService; View: BatteryView, ChevronView, ConnectionView, ContentView, PreviewView.
• Protocols: OutputService, DockAccessoryTrackingDelegate, CameraCaptureDelegate, DockController, PreviewSource, PreviewTarget, Camera.
• Methods: updateConfiguration, setVideoRotationAngle, getVideoRotationAngle, update, track, startOrStartCapture, switchCamera, zoom.
• Files: DockKitCamera/Preview Content/PreviewCameraModel.swift, DockKitCamera/Views/CameraPreview.swift, DockKitCamera/CaptureService.swift, DockKitCamera/ContentView.swift, DockKitCamera/DockControlService.swift, DockKitCamera/Model/CameraModel.swift.

Architecture takeaways

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