Implementing a store in your app using the StoreKit API

At a glance

Project structure

Source bundle/
├── SKDemo/
│   ├── SKDemoApp.swift
│   ├── In App Purchase/
│   │   └── Store.swift
│   ├── View/
│   │   ├── ContentView.swift
│   │   ├── Miscellaneous/
│   │   │   ├── CarItemStore.swift
│   │   │   └── ImageNameConstants.swift
│   │   ├── Stores/
│   │   │   ├── BoostStore.swift
│   │   │   └── SubscriptionStore.swift
│   │   ├── SelectedCarView.swift
│   │   └── SwiftUIMerchandisingView.swift
│   └── Model/
│       └── SKDemoPlusStatus.swift
└── SKDemoServer/
    └── Sources/
        ├── Consumable.swift
        └── Server.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 5 project/configuration file(s) and 62 source declaration(s).

Overall architecture

flowchart LR
    N1["SKDemoApp"]
    N2["ContentView"]
    N3["BoostStore"]
    N4["StoreKit APIs"]
    N1 --> N2
    N2 --> N3
    N3 --> N4

Reference code

SKDemo/SKDemoApp.swift:13 — architecture anchor

@main
struct SKDemoApp: App {
    var body: some Scene {
        WindowGroup {
            ContentView()
                .checkCustomerEntitlements()
                .loadProducts()
                .observeErrors()
        }
    }
}

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 StoreKit.

Ownership and state

classDiagram
    CustomerEntitlementsViewModifier *-- Logger : logger
    CustomerEntitlementsViewModifier *-- SKDemoPlusStatus : skDemoPlusStatus
    CustomerEntitlementsViewModifier *-- Set : ownedCars
    ErrorObserverViewModifier *-- Error : error

Ownership evidence

SKDemo/SKDemoApp.swift:31 — stored dependency or nearest verified ownership anchor

private struct CustomerEntitlementsViewModifier: ViewModifier {
    private let logger = Logger(subsystem: "SKDemo", category: "CustomerEntitlementsViewModifier")
    // ...
}

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

SKDemo/In App Purchase/CustomerEntitlements.swift:14 — representative execution boundary

@MainActor @Observable
public final class CustomerEntitlements {
    // ...
    private var transactionUpdatesTask: Task<Void, any Error>?
    // ...
}

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

SKDemo/SKDemoApp.swift:14 — representative type boundary

@main
struct SKDemoApp: App {
    // ...
            ContentView()
    // ...
}

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

Access control

Reference code

SKDemo/In App Purchase/CustomerEntitlements.swift:12 — representative boundary

private let logger = Logger(subsystem: "SKDemo", category: "CustomerEntitlements")

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: SKDemoApp; Store: BoostStore, CarItemStore, CarWashStore, FuelStore, Store; View: ActiveUpfrontView, CommitmentProgressView, ContentView, CustomProductView, PricingTermsView.
• Protocols: no local protocol declaration in the scanned source.
• Methods: body, checkCurrentUserState, observeEntitlementUpdates, transformOwnedNonConsumables, transformStatuses, checkCustomerEntitlements, loadProducts, observeErrors.
• Files: SKDemo/SKDemoApp.swift, SKDemo/In App Purchase/Store.swift, SKDemo/View/ContentView.swift, SKDemo/View/Miscellaneous/CarItemStore.swift, SKDemo/View/Stores/BoostStore.swift, SKDemo/View/Stores/SubscriptionStore.swift.

Architecture takeaways

• SKDemoApp is the main source-visible entry or composition anchor for this sample.
• Framework work reaches SwiftUI, StoreKit, SKDemoServer, SwiftData 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