Getting motion-activity data from headphones

At a glance

Project structure

Source bundle/
├── HeadphoneActivity/
│   ├── HeadphoneActivityApp.swift
│   ├── ContentView.swift
│   └── ContentViewState.swift
├── Configuration/
│   └── SampleCode.xcconfig
└── HeadphoneActivity.xcodeproj/
    ├── .xcodesamplecode.plist
    └── project.pbxproj

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 3 source declaration(s).

Overall architecture

flowchart LR
    N1["HeadphoneActivityApp"]
    N2["ContentView"]
    N3["CoreMotion APIs"]
    N1 --> N2
    N2 --> N3

Reference code

HeadphoneActivity/HeadphoneActivityApp.swift:10 — architecture anchor

@main
struct HeadphoneActivityApp: 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 Core Motion.

Ownership and state

classDiagram
    ContentView *-- ContentViewState : contentViewState
    ContentViewState *-- CMHeadphoneActivityManager : headphoneActivityManager
    ContentViewState *-- String : activity
    ContentViewState *-- Bool : isEnabled

Ownership evidence

HeadphoneActivity/ContentView.swift:12 — stored dependency or nearest verified ownership anchor

struct ContentView: View {
    // ...
    @StateObject private var contentViewState = ContentViewState()
    // ...
}

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

HeadphoneActivity/HeadphoneActivityApp.swift:11 — representative type boundary

struct HeadphoneActivityApp: App {
    var body: some Scene {
        WindowGroup {
            ContentView()
        }
    }
}

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

Access control

Reference code

HeadphoneActivity/ContentView.swift:12 — representative boundary

struct ContentView: View {
    // ...
    @StateObject private var contentViewState = ContentViewState()
    // ...
}

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: HeadphoneActivityApp; View: ContentView.
• Protocols: no local protocol declaration in the scanned source.
• Methods: activityHumanReadableDescription, startUpdating, stopUpdating.
• Files: HeadphoneActivity/HeadphoneActivityApp.swift, HeadphoneActivity/ContentView.swift, HeadphoneActivity/ContentViewState.swift.

Architecture takeaways

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