VoIP calling with CallKit

At a glance

Project structure

Source bundle/
├── Speakerbox-Watch/
│   ├── Speakerbox_WatchApp.swift
│   ├── ContentView.swift
│   └── PushRegistryDelegate.swift
├── Speakerbox/
│   ├── AppDelegate.swift
│   ├── AudioController.mm
│   ├── NewCallView.swift
│   ├── AudioController.h
│   ├── CallView.swift
│   ├── CallsListView.swift
│   ├── EmptyCallsView.swift
│   └── MainView.swift
└── IntentsExtension/
    └── IntentHandler.swift

Structure observations

• Architecturally prominent files are ranked from entry points and role-named declarations; resource-only paths are omitted.
• Primary languages: C++, C/Objective-C header, Objective-C++, Swift.
• The verified tree contains 8 project/configuration file(s) and 22 source declaration(s).

Overall architecture

flowchart LR
    Bundle["Sample bundle"]
    V1["Speakerbox-Watch"]
    V2["Speakerbox"]
    Boundary["CallKit APIs"]
    Bundle --> V1
    V1 --> Boundary
    Bundle --> V2
    V2 --> Boundary

Reference code

Speakerbox-Watch/Speakerbox_WatchApp.swift:11 — architecture anchor

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

Interpretation

The branches represent separate entry-bearing project variants in the downloaded bundle, not runtime calls between those variants. Each branch is intentionally collapsed at the documented framework boundary; the detailed target-local flow remains in the cited files. Ownership is claimed only where the next section cites a stored property or assignment.

Ownership and state

classDiagram
    SpeakerboxWatchApp *-- ProviderDelegate : callProvider
    ContentView o-- Callback : incomingCallback
    AppDelegate *-- PKPushRegistry : pushRegistry
    AppDelegate *-- SpeakerboxCallManager : callManager

Ownership evidence

Speakerbox-Watch/Speakerbox_WatchApp.swift:14 — stored dependency or nearest verified ownership anchor

@main
struct SpeakerboxWatchApp: App {
    // ...
    var callProvider = ProviderDelegate(callManager: SpeakerboxCallManager())
    // ...
}

Speakerbox/AppDelegate.swift:18 — iOS target dependencies

    let pushRegistry = PKPushRegistry(queue: .main)
    let callManager = SpeakerboxCallManager()
    var providerDelegate: ProviderDelegate?

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

Speakerbox/StartCallConvertible.swift:8 — representative type boundary

protocol StartCallConvertible {

    var startCallHandle: String? { get }
    var video: Bool? { get }

}

The source explicitly defines local protocol relationships: NSUserActivity → StartCallConvertible, URL → StartCallConvertible.

Access control

Reference code

Speakerbox-Watch/PushRegistryDelegate.swift:13 — representative boundary

    private let pushRegistry = PKPushRegistry(queue: DispatchQueue.main)

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: SpeakerboxWatchApp; Controller: AudioController; Delegate: AppDelegate, ProviderDelegate, PushRegistryDelegate, SceneDelegate; Handler: IntentHandler; Manager: SpeakerboxCallManager; View: CallView, CallsListView, ContentView, EmptyCallsView, MainView.
• Protocols: StartCallConvertible.
• Methods: application, pushRegistry, displayIncomingCall, setupAudioSession, setupIOUnit, setupAudioChain, init, handleInterruption.
• Files: Speakerbox-Watch/ContentView.swift, Speakerbox/AppDelegate.swift, Speakerbox/AudioController.mm, Speakerbox/NewCallView.swift, IntentsExtension/IntentHandler.swift, Speakerbox-Watch/PushRegistryDelegate.swift.

Architecture takeaways

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