Implemented the AudioTranscribingService service in the Sample app target.

Apps/Attendi/AudioTranscribingService.swift

@@ -0,0 +1,81 @@
+import AVFoundation
+import Recording
+import Speech
+
+/// The transcribing service used by the Attendi sample app, which transcribes recorded audio into text on device.
+///
+/// The service writes the recorded audio into a temporary `.m4a` file and runs it through a `SpeechAnalyzer` with a `SpeechTranscriber`
+/// module, joining the finalized results into the returned text. The speech model assets for the current locale are downloaded and installed
+/// on first use; every transcription after that happens entirely offline.
+struct AudioTranscribingService: TranscribingService {
+
+    // MARK: Initializers
+
+    /// Creates a speech transcribing service.
+    init() {}
+
+    // MARK: Methods
+
+    /// Transcribes the given recorded audio into text, deleting the temporary audio file when the transcription finishes.
+    ///
+    /// - Parameter audio: The recorded audio to transcribe.
+    /// - Returns: The transcription of the recorded audio.
+    /// - Throws: ``AudioTranscribingError/localeNotSupported`` when the transcriber does not support the current locale, or any
+    /// error thrown while installing the speech model assets, reading the audio file, or analyzing its contents.
+    func transcribe(_ audio: Data) async throws -> String {
+        try audio.write(to: Constant.File.url)
+
+        defer {
+            try? FileManager.default.removeItem(at: Constant.File.url)
+        }
+
+        guard let locale = await SpeechTranscriber.supportedLocale(equivalentTo: .current) else {
+            throw AudioTranscribingError.localeNotSupported
+        }
+
+        let transcriber = SpeechTranscriber(
+            locale: locale,
+            preset: .transcription
+        )
+
+        if let request = try await AssetInventory.assetInstallationRequest(supporting: [transcriber]) {
+            try await request.downloadAndInstall()
+        }
+
+        let analyzer = SpeechAnalyzer(modules: [transcriber])
+
+        async let text = transcriber.results.reduce(into: "") { text, result in
+            text += String(result.text.characters)
+        }
+
+        let file = try AVAudioFile(forReading: Constant.File.url)
+
+        if let lastSampleTime = try await analyzer.analyzeSequence(from: file) {
+            try await analyzer.finalizeAndFinish(through: lastSampleTime)
+        } else {
+            await analyzer.cancelAndFinishNow()
+        }
+
+        return try await text
+    }
+
+}
+
+// MARK: - Errors
+
+/// The errors thrown by ``AudioTranscribingService``.
+enum AudioTranscribingError: Error {
+    /// The transcriber does not support the current locale.
+    case localeNotSupported
+}
+
+// MARK: - Constants
+
+/// The constant values used across the speech transcribing service.
+private nonisolated enum Constant {
+    /// The file constants.
+    enum File {
+        /// The location of the temporary file the recorded audio is written into for the analysis.
+        static let url = FileManager.default.temporaryDirectory.appending(path: "transcription.m4a")
+    }
+}

Apps/Attendi/ContentView.swift

@@ -8,11 +8,11 @@ struct ContentView: View {
 
     // MARK: Body
 
-    /// The content of the view: the recording feature's view, attached to the microphone-backed recording service and the simulated transcribing service.
+    /// The content of the view: the recording feature's view, attached to the microphone-backed recording service and the on-device speech transcribing service.
     var body: some View {
         RecordingView(
             recorder: AudioRecordingService(),
-            transcriber: SimulatedTranscribingService()
+            transcriber: AudioTranscribingService()
         )
     }
 

Attendi.xcodeproj/project.pbxproj

@@ -24,6 +24,7 @@
 				Attendi/Assets.xcassets,
 				Attendi/AttendiApp.swift,
 				Attendi/AudioRecordingService.swift,
+				Attendi/AudioTranscribingService.swift,
 				Attendi/ContentView.swift,
 			);
 			target = 02870A0C2FF7EB610079EA3A /* Attendi */;