Recognizing speech in live audio

At a glance

Project structure

Source bundle/
├── SpokenWord/
│   ├── AppSceneDelegate.swift
│   ├── ViewController.swift
│   ├── Transcription.swift
│   ├── Base.lproj/
│   │   └── Main.storyboard
│   └── Info.plist
├── datagenerator/
│   └── main.swift
├── Configuration/
│   └── SampleCode.xcconfig
└── SpokenWord.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 5 project/configuration file(s) and 7 source declaration(s).

Overall architecture

flowchart LR
    N1["AppSceneDelegate"]
    N2["ViewController"]
    N3["IsolatedCaptureSession"]
    N4["Speech APIs"]
    N1 --> N2
    N2 --> N3
    N3 --> N4

Reference code

SpokenWord/AppSceneDelegate.swift:10 — architecture anchor

@main
class AppDelegate: UIResponder, UIApplicationDelegate {
}

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 Speech.

Ownership and state

classDiagram
    SceneDelegate o-- UIWindow : window
    main o-- DictationTranscriber : locale
    main *-- SFCustomLanguageModelData : data
    ViewController o-- UITextView : textView

Ownership evidence

SpokenWord/AppSceneDelegate.swift:15 — stored dependency or nearest verified ownership anchor

class SceneDelegate: UIResponder, UIWindowSceneDelegate {
    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

SpokenWord/Transcription.swift:51 — representative execution boundary

@MainActor
final class SpokenWordTranscriber {
    private var transcriber: DictationTranscriber?
    // ...
}

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

SpokenWord/AppSceneDelegate.swift:11 — representative type boundary

@main
class AppDelegate: UIResponder, UIApplicationDelegate {
}

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

Access control

Reference code

SpokenWord/Transcription.swift:53 — representative boundary

@MainActor
final class SpokenWordTranscriber {
    private var transcriber: DictationTranscriber?
    // ...
}

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

Main application flow

sequenceDiagram
    participant ViewController
    participant captureSession
    participant MainActor
    participant transcriber
    ViewController->>captureSession: startRunning()
    ViewController->>MainActor: Run UI-isolated work
    ViewController->>transcriber: transcribeAudio()
    ViewController->>captureSession: stopRunning()
    ViewController->>MainActor: Run UI-isolated work

Reference code

SpokenWord/ViewController.swift:213 — captureAndAnalyzeAudio()

    private func captureAndAnalyzeAudio(
        transcriber: SpokenWordTranscriber,
        captureSession: IsolatedCaptureSession,
        audioSequence: any AsyncSequence<AnalyzerInput, any Error> & Sendable
    ) async throws {
        if await captureSession.startRunning() {
            await MainActor.run {
                self.updateUI(captureIsRunning: true)
            }

            // Returns when task is canceled
            try await transcriber.transcribeAudio(audioSequence)

            await captureSession.stopRunning()
            await MainActor.run {
                self.updateUI(captureIsRunning: false)
            }
        }
    }

Naming conventions

• Types: Controller: ViewController; Delegate: AppDelegate, SceneDelegate; Session: IsolatedCaptureSession.
• Protocols: no local protocol declaration in the scanned source.
• Methods: viewDidLoad, viewDidAppear, prepareEnvironment, startRecording, runSession, captureAndAnalyzeAudio, updateTranscription, stopRecording.
• Files: SpokenWord/ViewController.swift.

Architecture takeaways

• AppSceneDelegate is the main source-visible entry or composition anchor for this sample.
• Framework work reaches Speech, UIKit, SwiftUI, Synchronization 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