Implemented the AudioRecordingService service in the Sample app target.

Apps/Attendi/AudioRecordingService.swift

@@ -0,0 +1,136 @@
+import AVFoundation
+import Recording
+
+/// The recording service used by the Attendi sample app, which captures real audio from the device's microphone.
+///
+/// The service records into a temporary `.m4a` file through an `AVAudioRecorder`, and returns the file's contents when the recording stops.
+/// The user's permission to record is requested before a recording starts and, on the platforms that require it, the shared audio session is
+/// configured for recording while the capture is in progress.
+@MainActor
+final class AudioRecordingService: RecordingService {
+
+    // MARK: Properties
+
+    /// The recorder that captures the audio from the microphone into a temporary file.
+    private var recorder: AVAudioRecorder?
+
+    // MARK: Initializers
+
+    /// Creates an audio recording service.
+    init() {}
+
+    // MARK: Methods
+
+    /// Starts a new audio recording from the microphone.
+    ///
+    /// - Throws: ``AudioRecordingError/permissionNotGranted`` when the user denies the app access to the microphone,
+    /// ``AudioRecordingError/captureNotStarted`` when the recorder fails to start, or any error thrown while configuring
+    /// the audio session or creating the recorder.
+    func start() async throws {
+        guard await AVAudioApplication.requestRecordPermission() else {
+            throw AudioRecordingError.permissionNotGranted
+        }
+
+        #if os(iOS) || os(visionOS)
+        let session = AVAudioSession.sharedInstance()
+
+        try session.setCategory(.record, mode: .default)
+        try session.setActive(true)
+        #endif
+
+        let recorder = try AVAudioRecorder(
+            url: Constant.File.url,
+            settings: Constant.Audio.settings
+        )
+
+        guard recorder.record() else {
+            throw AudioRecordingError.captureNotStarted
+        }
+
+        self.recorder = recorder
+    }
+
+    /// Pauses the ongoing recording.
+    ///
+    /// - Throws: ``AudioRecordingError/noOngoingRecording`` when no recording is in progress.
+    func pause() async throws {
+        guard let recorder else {
+            throw AudioRecordingError.noOngoingRecording
+        }
+
+        recorder.pause()
+    }
+
+    /// Resumes a paused recording.
+    ///
+    /// - Throws: ``AudioRecordingError/noOngoingRecording`` when no recording is in progress, or
+    /// ``AudioRecordingError/captureNotStarted`` when the recorder fails to resume.
+    func resume() async throws {
+        guard let recorder else {
+            throw AudioRecordingError.noOngoingRecording
+        }
+        guard recorder.record() else {
+            throw AudioRecordingError.captureNotStarted
+        }
+    }
+
+    /// Stops the recording, deleting the temporary audio file after its contents are read.
+    ///
+    /// - Returns: The audio captured since the recording started.
+    /// - Throws: ``AudioRecordingError/noOngoingRecording`` when no recording is in progress, or any error thrown
+    /// while reading the recorded audio file.
+    func stop() async throws -> Data {
+        guard let recorder else {
+            throw AudioRecordingError.noOngoingRecording
+        }
+
+        recorder.stop()
+
+        self.recorder = nil
+
+        #if os(iOS) || os(visionOS)
+        try? AVAudioSession.sharedInstance().setActive(false)
+        #endif
+
+        defer {
+            try? FileManager.default.removeItem(at: Constant.File.url)
+        }
+
+        return try Data(contentsOf: Constant.File.url)
+    }
+
+}
+
+// MARK: - Errors
+
+/// The errors thrown by ``AudioRecordingService``.
+enum AudioRecordingError: Error {
+    /// The recorder failed to start or resume the audio capture.
+    case captureNotStarted
+    /// No recording is in progress.
+    case noOngoingRecording
+    /// The user denied the app permission to record audio from the microphone.
+    case permissionNotGranted
+}
+
+// MARK: - Constants
+
+/// The constant values used across the audio recording service.
+private enum Constant {
+    /// The audio constants.
+    enum Audio {
+        /// The settings of the recorded audio: single-channel AAC at a 44.1 kHz sample rate, encoded in high quality.
+        static let settings: [String: Any] = [
+            AVFormatIDKey: kAudioFormatMPEG4AAC,
+            AVNumberOfChannelsKey: 1,
+            AVSampleRateKey: 44_100.0,
+            AVEncoderAudioQualityKey: AVAudioQuality.high.rawValue,
+        ]
+    }
+
+    /// The file constants.
+    enum File {
+        /// The location of the temporary file the audio is captured into.
+        static let url = FileManager.default.temporaryDirectory.appending(path: "recording.m4a")
+    }
+}

Apps/Attendi/ContentView.swift

@@ -8,10 +8,10 @@ struct ContentView: View {
 
     // MARK: Body
 
-    /// The content of the view: the recording feature's view, attached to the simulated recording and transcribing services.
+    /// The content of the view: the recording feature's view, attached to the microphone-backed recording service and the simulated transcribing service.
     var body: some View {
         RecordingView(
-            recorder: SimulatedRecordingService(),
+            recorder: AudioRecordingService(),
             transcriber: SimulatedTranscribingService()
         )
     }

Attendi.xcodeproj/project.pbxproj

@@ -23,6 +23,7 @@
 			membershipExceptions = (
 				Attendi/Assets.xcassets,
 				Attendi/AttendiApp.swift,
+				Attendi/AudioRecordingService.swift,
 				Attendi/ContentView.swift,
 			);
 			target = 02870A0C2FF7EB610079EA3A /* Attendi */;