A sample app that implements an audio recording flow in SwiftUI: start, pause, resume, or discard a recording while a timer tracks the elapsed time, then send the recording to be transcribed on device — and read the resulting text in a sheet.

Context

This sample app was created for a technical interview for a senior Mobile (iOS + Android) engineer role at Attendi, a Dutch health-tech company that makes voice-driven reporting software for healthcare professionals, based on a given set of requirements.

Requirements

Requirement	Version
Xcode	26 or later
Swift	6.3
Platforms	iOS/macOS/visionOS 26

Project structure

The project separates the app shell from the feature code, which lives in a local Swift package:

Attendi/
├── Attendi.xcodeproj
├── Apps/
│   └── Attendi/                         # The app target (thin shell)
│       ├── App/                         # The @main entry point
│       ├── Views/                       # The root view: hosts the feature, the locale picker, and the transcription sheet
│       ├── View Models/                 # The services, the supported locales, and the speech model preinstallation
│       ├── Catalogs/                    # The app's assets and localized strings
│       └── Resources/                   # The Info.plist, including the microphone usage description
└── Packages/
    └── Features/                        # Local Swift package with the feature code
        ├── Package.swift
        ├── Sources/
        │   └── Recording/               # The Recording feature target
        │       ├── Catalogs/            # The record, pause, and send icons; the localized strings
        │       ├── Models/              # Transcription, RecordingError
        │       ├── Protocols/           # Capturing, Transcribing
        │       ├── Services/            # AudioCapturing, AudioTranscribing, and their development dummies
        │       ├── Styles/              # RecordingButtonStyle
        │       ├── View Models/         # RecordingViewModel
        │       └── Views/               # RecordingView
        └── Tests/
            ├── Recording/               # The model and view model suites, with their mocks
            └── Features.xctestplan

The app target only depends on the Features package and renders its public RecordingView view; all recording logic and UI live in the package's Recording target.

The Recording feature

State machine

The flow is modeled as a state machine in RecordingView.Model, an @Observable, @MainActor view model:

State	Meaning
`notRecording`	Idle; no recording in progress.
`recording`	A recording is in progress and the timer is ticking.
`paused`	The recording is paused; it can be resumed, discarded, or sent.
`processing`	The sent recording is being stopped and transcribed.

The main button starts, pauses, and resumes a recording. While paused, two more buttons appear: discard throws the recording away, and send moves the flow into processing — stopping the capture and transcribing the audio — before returning to idle. The model owns every side effect of a transition (timer, capture, processing), so the state machine works the same whether it is driven by the view's buttons or by the unit tests.

The calls to the capturing service are serialized through a task chain: no matter how quickly the states change, start, pause, resume, and stop always reach the service in order. When the system interrupts the audio session mid-recording — a phone call or Siri, for example — the service emits an event and the model pauses exactly like a press of the main button would; the capture is never resumed without the user asking for it.

Timer

The recording time is measured with a monotonic ContinuousClock: an anchor marks the start of the current recording stretch, and pausing folds the stretch into an accumulated duration, so scheduling latency never accumulates as drift. While recording, an async task republishes the measured time once per second. The view formats the count as mm:ss and animates digit changes with a numeric text content transition.

Errors

Failures of either service are published by the model as a RecordingError and presented by the view in an alert: a denied microphone permission additionally offers to open the app's settings, and unavailable speech model assets are distinguished from an ordinary transcription failure. The underlying errors are logged through OSLog under the Features.Recording subsystem.

Views

RecordingView — the public entry point of the feature. It renders the timer label and the control buttons for the model's current state, forwards every transcription to a closure given at initialization, and presents the error alert. All controls carry localized accessibility labels matching their current action, and the timer exposes its value to assistive technologies spelled out in full units.
RecordingButtonStyle — a custom ButtonStyle used by the controls: the label sits on a padded, circular red Liquid Glass background that reacts fluidly to presses, and dims while disabled. The label and its padding scale with Dynamic Type via @ScaledMetric, and an invertStyle flag controls whether the label's color scheme is inverted for contrast.

Services

The actual recording work is abstracted behind two protocols, injected into RecordingView at initialization and attached to its view model:

Capturing — captures the audio from a microphone, with throwing async start, pause, resume, and stop methods; stop hands the captured audio over as a file URL, avoiding any in-memory copies. An events stream (empty by default) lets a service report interruptions of the capture.
Transcribing — a callable service that transcribes a recorded audio file into text for a given locale, returning a Transcription.

The real backends used by the app are:

AudioCapturing — records single-channel AAC into a temporary file through AVAudioRecorder, requesting the microphone permission and managing the shared audio session on the platforms that require it, and emitting an event when the system interrupts the session while recording.
AudioTranscribing — transcribes entirely on device through SpeechAnalyzer with a SpeechTranscriber module, in the closest supported equivalent of the requested locale, installing any missing speech model assets before the analysis.

The internal DummyCapturing and DummyTranscribing fake the work for previews and default model values (the latter with a two-second delay and a dummy transcription); the unit tests inject configurable mocks, and other backends can be plugged in the same way without touching the feature's state machine.

The app shell

ContentView hosts the feature inside a navigation stack and presents the transcribed text of every processed recording in a modal sheet — or a content-unavailable message when the transcription is empty. A toolbar menu picks the locale of the spoken language from the locales the transcriber supports, aligned at launch with the closest supported equivalent of the user's locale. Picking a locale preinstalls its speech model assets in the background, so the first transcription does not have to download them mid-processing; the app keeps a single asset locale reservation at a time, releasing stale ones, since the system only permits a limited number per app.

Testing

The package is covered by Swift Testing suites: RecordingViewModelTests.swift groups the view model's behaviors with nested @Suite types (initial state, button presses, computed properties, timer, capturer, errors, interruptions, and processing), and TranscriptionTests.swift covers the Transcription model. The state-dependent behaviors are exercised with parameterized tests across all four states, driven through the model's public press handlers, and the service mocks record their invocations in call order.

Run the tests with the Features scheme in Xcode (⌘U), or from the command line:

xcodebuild test -scheme Features -destination 'platform=iOS'

Localization

Both the app and the feature package localize their user-facing text through string catalogs (Localizable.xcstrings, currently English only): the app's catalog covers the navigation titles and the transcription sheet, and the package's catalog covers the error alert and the accessibility labels.

Tooling

.swift-format — configuration for Apple's swift-format, used by Xcode's built-in formatter (4-space indentation, 200-column lines).