Integrating CarPlay with your quick-ordering app

At a glance

Project structure

Source bundle/
└── Hoagies/
    ├── HoagiePushServer/
    │   ├── HoagiePushServerApp.swift
    │   └── ContentView.swift
    ├── Hoagies/
    │   ├── HoagiesApp.swift
    │   ├── ContentView.swift
    │   ├── CarPlay/
    │   │   ├── AppDelegate.swift
    │   │   ├── TemplateManager.swift
    │   │   ├── CarPlayTemplateApplicationSceneDelegate.swift
    │   │   └── SceneDelegate.swift
    │   └── OrderingService.swift
    ├── OrderStatus/
    │   ├── OrderStatusBundle.swift
    │   └── OrderStatus.swift
    └── Shared/
        └── FalseData.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 8 project/configuration file(s) and 44 source declaration(s).

Overall architecture

flowchart LR
    N1["HoagiePushServerApp"]
    N2["ContentView"]
    N3["TemplateManager"]
    N4["OrderingService"]
    N5["CarPlay APIs"]
    N1 --> N2
    N2 --> N3
    N3 --> N4
    N4 --> N5

Reference code

Hoagies/HoagiePushServer/HoagiePushServerApp.swift:9 — architecture anchor

@main
struct HoagiePushServerApp: App {
    var body: some Scene {
        WindowGroup {
            ContentView()
        }
    }
}

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 CarPlay.

Ownership and state

classDiagram
    ContentView o-- MemoryLogger : shared
    PickBreadView *-- Hoagie : hoagie
    PickMeatsView *-- Hoagie : hoagie
    CheeseView *-- Hoagie : hoagie

Ownership evidence

Hoagies/Hoagies/ContentView.swift:12 — stored dependency or nearest verified ownership anchor

struct ContentView: View {
    // ...
    @Bindable var shared: MemoryLogger
    // ...
}

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

Hoagies/HoagiePushServer/APNS.swift:122 — representative execution boundary

    static func sendLiveActivityContent(
        // ...
        order: TestHoagieData.HoagieOrder? = nil) async throws {
        // ...
    }

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

Hoagies/Hoagies/CarPlay/Logger.swift:21 — representative type boundary

protocol Logger {
    /// Append a new event to the log. The system adds all events at the 0 index.
    func appendEvent(_: String)

    /// Fetch the list of events that this logger receives.
    var events: [Event] { get }
}

The source explicitly defines local protocol relationships: MemoryLogger → Logger.

Access control

Reference code

Hoagies/HoagiePushServer/APNS.swift:23 — representative boundary

final class APNS {
    // ...
    private static let apnsTopic = "<Bundle ID>.push-type.liveactivity"

    // ...
}

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: HoagiePushServerApp, HoagiesApp; Delegate: AppDelegate, CarPlayTemplateApplicationSceneDelegate, SceneDelegate; Manager: TemplateManager; Provider: Provider; Service: OrderingService; View: CheeseView, ContentView, OrderStatusEntryView, OrderStatusView, PickBreadView.
• Protocols: Logger.
• Methods: saveLastOrder, houseFavoriteOrder, lastOrder, testMapItems, application, applicationDidBecomeActive, applicationWillResignActive, applicationDidEnterBackground.
• Files: Hoagies/HoagiePushServer/HoagiePushServerApp.swift, Hoagies/Hoagies/HoagiesApp.swift, Hoagies/Hoagies/ContentView.swift, Hoagies/OrderStatus/OrderStatusBundle.swift, Hoagies/Hoagies/CarPlay/AppDelegate.swift, Hoagies/Hoagies/CarPlay/TemplateManager.swift.

Architecture takeaways

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