Reading and Writing HealthKit Series Data

At a glance

Project structure

Source bundle/
├── HeartDogs/
│   ├── AppDelegate.swift
│   ├── GameControllerHeartSensorSession.swift
│   ├── GameViewController.swift
│   ├── DetailViewController.swift
│   ├── HistoryViewController.swift
│   ├── Detailable.swift
│   ├── HealthStoreContainer.swift
│   ├── HKHeartbeatSeriesSample+Detailable.swift
│   ├── HKStatistics+Detailable.swift
│   └── UIViewController+Enumerate.swift
├── Configuration/
│   └── SampleCode.xcconfig
└── HeartDogs.xcodeproj/
    └── .xcodesamplecode.plist

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 9 source declaration(s).

Overall architecture

flowchart LR
    N1["AppDelegate"]
    N2["DetailViewController"]
    N3["GameControllerHeartSensorSession"]
    N4["HealthKit APIs"]
    N1 --> N2
    N2 --> N3
    N3 --> N4

Reference code

HeartDogs/AppDelegate.swift:11 — architecture anchor

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

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
    AppDelegate o-- HKHealthStore : healthStore
    GameControllerHeartSensorSession *-- NSUUID : UUID
    GameControllerHeartSensorSession *-- Date : startDate

Ownership evidence

HeartDogs/AppDelegate.swift:14 — 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.

Class and protocol design

HeartDogs/GameControllerHeartSensorSession.swift:11 — representative type boundary

protocol GameControllerHeartSensorSessionDelegate: AnyObject {
    func sessionDidStart(_ session: GameControllerHeartSensorSession, startDate: Date)
    func sessionDidReceiveHeartRate(_ session: GameControllerHeartSensorSession, heartRate: HKQuantity, dateInterval: DateInterval)
    func sessionDidReceiveHeartBeat(_ session: GameControllerHeartSensorSession, timeIntervalSinceStart: TimeInterval, precededByGap: Bool)
    func sessionDidEnd(_ session: GameControllerHeartSensorSession, endDate: Date)
}

The source explicitly defines local protocol relationships: DetailViewController → HealthStoreContainer, GameViewController → HealthStoreContainer, GameViewController → GameControllerHeartSensorSessionDelegate, HistoryViewController → HealthStoreContainer, HKHeartbeatSeriesSample → Detailable, HKStatistics → Detailable.

Access control

Reference code

HeartDogs/AppDelegate.swift:16 — representative boundary

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {
    // ...
    private let healthStore: HKHealthStore
    // ...
}

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: DetailViewController, GameViewController, HistoryViewController; Delegate: AppDelegate, GameControllerHeartSensorSessionDelegate; Session: GameControllerHeartSensorSession.
• Protocols: GameControllerHeartSensorSessionDelegate, Detailable, HealthStoreContainer.
• Methods: application, sessionDidStart, sessionDidReceiveHeartRate, sessionDidReceiveHeartBeat, sessionDidEnd, start, finish, generateSimulatedHeartData.
• Files: HeartDogs/AppDelegate.swift, HeartDogs/GameControllerHeartSensorSession.swift, HeartDogs/GameViewController.swift, HeartDogs/DetailViewController.swift, HeartDogs/HistoryViewController.swift, HeartDogs/Detailable.swift.

Architecture takeaways

• AppDelegate is the main source-visible entry or composition anchor for this sample.
• Framework work reaches HealthKit, UIKit 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