Creating a Mobility Health App

At a glance

Project structure

Source bundle/
└── SmoothWalker/
    ├── AppDelegate.swift
    ├── Data/
    │   ├── HealthData.swift
    │   └── Network.swift
    ├── Models/
    │   └── ServerResponse.swift
    └── Interface/
        ├── Table View Controllers/
        │   ├── DataTableViewController.swift
        │   ├── HealthDataTableViewController.swift
        │   ├── ChartTableViewController.swift
        │   └── HealthQueryTableViewController.swift
        ├── View Controllers/
        │   └── SplashScreenViewController.swift
        ├── Collection View Controllers/
        │   └── FeedItemViewController.swift
        ├── Tab View Controllers/
        │   └── MainTabViewController.swift
        └── Views/
            └── EmptyDataBackgroundView.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 7 project/configuration file(s) and 30 source declaration(s).

Overall architecture

flowchart LR
    N1["AppDelegate"]
    N2["ChartTableViewController"]
    N3["HealthKit APIs"]
    N1 --> N2
    N2 --> N3

Reference code

SmoothWalker/AppDelegate.swift:10 — architecture anchor

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {
    // ...
    var window: UIWindow?
    // ...
}

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 HealthKit.

Ownership and state

classDiagram
    AppDelegate o-- UIWindow : window
    HealthData *-- HKHealthStore : healthStore
    ServerResponse *-- String : identifier
    ServerResponse *-- Date : date

Ownership evidence

SmoothWalker/AppDelegate.swift:13 — stored dependency or nearest verified ownership anchor

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {
    // ...
    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

SmoothWalker/Interface/Table View Controllers/HealthDataTableViewController.swift:109 — representative execution boundary

                DispatchQueue.main.async {
                    self?.updateNavigationItem()
                }

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

SmoothWalker/Interface/Table View Controllers/DataTableViewController.swift:11 — representative type boundary

protocol HealthQueryDataSource: AnyObject {
    /// Create and execute a query on a health store. Note: The completion handler returns on a background thread.
    func performQuery(completion: @escaping () -> Void)
}

The source explicitly defines local protocol relationships: HealthQueryTableViewController → HealthQueryDataSource, WeeklyQuantitySampleTableViewController → HealthQueryDataSource, WelcomeViewController → SplashScreenViewControllerDelegate, HealthDataTableViewController → HealthDataTableViewControllerDelegate.

Access control

Reference code

SmoothWalker/Cells/FeedItemCollectionViewCell.swift:40 — representative boundary

    private func setUpView() {
        contentView.addSubview(chartView)

        setUpConstraints()
    }

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: Controller: ChartTableViewController, DataTableViewController, DataTypeCollectionViewController, HealthDataTableViewController, HealthQueryTableViewController; DataSource: HealthQueryDataSource; Delegate: AppDelegate, HealthDataTableViewControllerDelegate, SceneDelegate, SplashScreenViewControllerDelegate; View: EmptyDataBackgroundView.
• Protocols: HealthQueryDataSource, HealthDataTableViewControllerDelegate, SplashScreenViewControllerDelegate.
• Methods: application, requestHealthDataAccessIfNeeded, saveHealthData, fetchStatistics, updateAnchor, anchorKey, getAnchor, setAnchor.
• Files: SmoothWalker/AppDelegate.swift, SmoothWalker/Data/HealthData.swift, SmoothWalker/Data/Network.swift, SmoothWalker/Models/ServerResponse.swift, SmoothWalker/Interface/Table View Controllers/DataTableViewController.swift, SmoothWalker/Interface/Table View Controllers/HealthDataTableViewController.swift.

Architecture takeaways

• AppDelegate is the main source-visible entry or composition anchor for this sample.
• Framework work reaches UIKit, HealthKit, CareKitUI 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.
• Local protocol relationships provide an explicit substitution boundary.

Source map

• Official Apple documentation