Measuring distance between devices using Channel Sounding

At a glance

Project structure

Source bundle/
├── CoreBluetooth-ChannelSounding/
│   ├── CoreBluetooth-ChannelSounding/
│   │   ├── AppDelegate.swift
│   │   ├── ContentView.swift
│   │   ├── BluetoothManager.swift
│   │   ├── SceneDelegate.swift
│   │   ├── ViewController.swift
│   │   ├── BluetoothManagerCoreBluetooth.swift
│   │   └── BluetoothManagerNearbyInteraction.swift
│   ├── CoreBluetooth-ChannelSoundingTests/
│   │   └── CoreBluetooth_ChannelSoundingTests.swift
│   ├── CoreBluetooth-ChannelSoundingUITests/
│   │   └── CoreBluetooth_ChannelSoundingUITests.swift
│   └── CoreBluetooth-ChannelSounding.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 7 project/configuration file(s) and 16 source declaration(s).

Overall architecture

flowchart LR
    N1["AppDelegate"]
    N2["ViewController"]
    N3["BluetoothManager"]
    N4["CoreBluetooth APIs"]
    N1 --> N2
    N2 --> N3
    N3 --> N4

Reference code

CoreBluetooth-ChannelSounding/CoreBluetooth-ChannelSounding/AppDelegate.swift:10 — architecture anchor

@main
class AppDelegate: UIResponder, UIApplicationDelegate {

    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
        // Override point for customization after application launch.
        return true
    }

    // MARK: UISceneSession Lifecycle

    func application(
        _ application: UIApplication,
        configurationForConnecting connectingSceneSession: UISceneSession,
        options: UIScene.ConnectionOptions
    ) -> UISceneConfiguration {
        // Called when a new scene session is being created.
        // Use this method to select a configuration to create the new scene with.
        return UISceneConfiguration(name: "Default Configuration", sessionRole: connectingSceneSession.role)
    }

    func application(_ application: UIApplication,
                     didDiscardSceneSessions sceneSessions: Set<UISceneSession>) {
        // Called when the person discards a scene session.
        // If the system discarded any sessions while the application wasn't running,
        // this will be called shortly after `application:didFinishLaunchingWithOptions`.
        // Use this method to release any resources specific to the discarded scenes.
    }

}

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 Bluetooth.

Ownership and state

classDiagram
    ContentView *-- BluetoothManager : bluetooth
    AccessorySetupView o-- BluetoothManager : bluetooth
    DeviceView o-- Bool : showDevice
    DeviceView o-- BluetoothManager : bluetooth

Ownership evidence

CoreBluetooth-ChannelSounding/CoreBluetooth-ChannelSounding/ContentView.swift:16 — stored dependency or nearest verified ownership anchor

struct ContentView: View {
    @StateObject private var bluetooth = BluetoothManager()
    // ...
}

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

CoreBluetooth-ChannelSounding/CoreBluetooth-ChannelSoundingTests/CoreBluetooth_ChannelSoundingTests.swift:13 — representative execution boundary

    @Test func example() async throws {
        // Write your test here and use APIs like `#expect(...)` to check expected conditions.
        // Swift Testing Documentation
        // https://developer.apple.com/documentation/testing
    }

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

CoreBluetooth-ChannelSounding/CoreBluetooth-ChannelSounding/AppDelegate.swift:11 — representative type boundary

@main
class AppDelegate: UIResponder, UIApplicationDelegate {
    // ...
        return true
    // ...
}

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

Access control

Reference code

CoreBluetooth-ChannelSounding/CoreBluetooth-ChannelSounding/BluetoothManager.swift:87 — representative boundary

final class BluetoothManager: NSObject, ObservableObject {
    // ...
    @Published private(set) var connectedPeripheral: CBPeripheral?
    // ...
}

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: Controller: ViewController; Delegate: AppDelegate, SceneDelegate; Manager: BluetoothManager; View: AccessorySetupView, ArrowView, ContentView, DeviceView.
• Protocols: no local protocol declaration in the scanned source.
• Methods: application, showAccessoryPicker, handleAccessoryEvent, connectAccessory, retrieveAndConnect, disconnect, startChannelSounding, stopChannelSounding.
• Files: CoreBluetooth-ChannelSounding/CoreBluetooth-ChannelSounding/AppDelegate.swift, CoreBluetooth-ChannelSounding/CoreBluetooth-ChannelSounding/ContentView.swift, CoreBluetooth-ChannelSounding/CoreBluetooth-ChannelSounding/BluetoothManager.swift, CoreBluetooth-ChannelSounding/CoreBluetooth-ChannelSounding/SceneDelegate.swift, CoreBluetooth-ChannelSounding/CoreBluetooth-ChannelSounding/ViewController.swift.

Architecture takeaways

• AppDelegate is the main source-visible entry or composition anchor for this sample.
• Framework work reaches CoreBluetooth, UIKit, NearbyInteraction, SwiftUI 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