Building a workout app for iPhone and iPad

At a glance

Project structure

Source bundle/
├── WorkoutsOniOSSampleApp/
│   ├── WorkoutsOniOSSampleApp.swift
│   ├── WorkoutsOniOSSampleAppDelegate.swift
│   ├── Views/
│   │   ├── MetricsView.swift
│   │   └── SummaryView.swift
│   ├── NavigationModel.swift
│   ├── WorkoutManager.swift
│   └── CountDownManager.swift
├── WorkoutWidget/
│   ├── WorkoutWidgetBundle.swift
│   ├── WorkoutWidgetViewModel.swift
│   └── LiveActivityView.swift
└── Shared/
    ├── ElapsedTimeView.swift
    └── MetricsModel.swift

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 6 project/configuration file(s) and 29 source declaration(s).

Overall architecture

flowchart LR
    Bundle["Sample bundle"]
    V1["WorkoutWidget"]
    V2["WorkoutsOniOSSampleApp"]
    Boundary["HealthKit APIs"]
    Bundle --> V1
    V1 --> Boundary
    Bundle --> V2
    V2 --> Boundary

Reference code

WorkoutsOniOSSampleApp/WorkoutsOniOSSampleApp.swift:10 — architecture anchor

@main
struct WorkoutsOniOSSampleApp: App {
    @UIApplicationDelegateAdaptor(WorkoutsOniOSSampleAppDelegate.self) var appDelegate
    // ...
}

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
    WorkoutsOniOSSampleApp *-- NavigationModel : navigationModel
    WorkoutWidgetViewModel *-- WorkoutWidgetViewModel : shared
    ActivityViewState o-- ActivityState : activityState
    ActivityViewState o-- ContentState : contentState

Ownership evidence

WorkoutsOniOSSampleApp/WorkoutsOniOSSampleApp.swift:14 — stored dependency or nearest verified ownership anchor

@main
struct WorkoutsOniOSSampleApp: App {
    // ...
    @State private var navigationModel = NavigationModel()
    // ...
}

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

WorkoutWidget/WorkoutWidgetViewModel.swift:12 — representative execution boundary

@Observable
@MainActor final class WorkoutWidgetViewModel {
    static let shared = WorkoutWidgetViewModel()
    // ...
}

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

WorkoutsOniOSSampleApp/WorkoutsOniOSSampleApp.swift:11 — representative type boundary

@main
struct WorkoutsOniOSSampleApp: App {
    @UIApplicationDelegateAdaptor(WorkoutsOniOSSampleAppDelegate.self) var appDelegate
    // ...
}

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

Access control

Reference code

Shared/ElapsedTimeView.swift:12 — representative boundary

struct ElapsedTimeView: View {
    // ...
    @State private var timeFormatter = ElapsedTimeFormatter()
    // ...
}

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: WorkoutsOniOSSampleApp; Delegate: WorkoutsOniOSSampleAppDelegate, WorkoutsOniOSSampleAppSceneDelegate; Handler: IntentHandler; Manager: CountDownManager, WorkoutManager; Model: MetricsModel, NavigationModel; View: ControlsView, CountDownView, ElapsedTimeView, LiveActivityView, MetricsView; ViewModel: WorkoutWidgetViewModel.
• Protocols: no local protocol declaration in the scanned source.
• Methods: startLiveActivity, updateLiveActivity, endLiveActivity, endActivity, setup, observeActivity, updateWorkoutLiveActivity, cleanUpDismissedActivity.
• Files: WorkoutsOniOSSampleApp/WorkoutsOniOSSampleApp.swift, WorkoutWidget/WorkoutWidgetBundle.swift, WorkoutWidget/WorkoutWidgetViewModel.swift, WorkoutsOniOSSampleApp/WorkoutsOniOSSampleAppDelegate.swift, WorkoutsOniOSSampleApp/Views/MetricsView.swift, Shared/ElapsedTimeView.swift.

Architecture takeaways

• WorkoutsOniOSSampleApp is the main source-visible entry or composition anchor for this sample.
• Framework work reaches SwiftUI, HealthKit, ActivityKit, WidgetKit 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