WWDC22 Challenge: Learn Switch Control through gaming

At a glance

Project structure

Source bundle/
├── SwitchControlChallenge/
│   ├── SwitchControlChallengeApp.swift
│   ├── Views/
│   │   ├── ContentView.swift
│   │   ├── GameBoardView.swift
│   │   ├── CardView.swift
│   │   └── Intro/
│   │       ├── IntroPage.swift
│   │       └── DescriptionPoint.swift
│   └── Models/
│       ├── Card.swift
│       ├── Deck.swift
│       ├── Game.swift
│       └── Symbol.swift
├── Configuration/
│   └── SampleCode.xcconfig
└── SwitchControlChallenge.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 3 project/configuration file(s) and 10 source declaration(s).

Overall architecture

flowchart LR
    N1["SwitchControlChallengeApp"]
    N2["ContentView"]
    N3["SwiftUI / UIKit APIs"]
    N1 --> N2
    N2 --> N3

Reference code

SwitchControlChallenge/SwitchControlChallengeApp.swift:10 — architecture anchor

@main
struct SwitchControlChallengeApp: 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 Accessibility.

Ownership and state

classDiagram
    GameBoardView *-- Game : viewModel
    CardView o-- Card : card
    Card *-- UUID : id
    Card o-- Symbol : symbol

Ownership evidence

SwitchControlChallenge/Views/GameBoardView.swift:14 — stored dependency or nearest verified ownership anchor

struct GameBoardView: View {
    // ...
    @StateObject var viewModel = Game(numberOfCards: Self.numberOfCards)
    // ...
}

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

SwitchControlChallenge/Models/Game.swift:42 — representative execution boundary

                Task { @MainActor in
                    score += 1
                    try await Task.sleep(nanoseconds: 1_000_000_000)
                    UIAccessibility.post(notification: .announcement, argument: "Found a match!")
                    deck.cards[requestedCardIndex].isMatched = true
                    deck.cards[currentlySelectedCardIndex].isMatched = true
                }

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

SwitchControlChallenge/SwitchControlChallengeApp.swift:11 — representative type boundary

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

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

Access control

Reference code

SwitchControlChallenge/Models/Game.swift:13 — representative boundary

class Game: ObservableObject {
    // ...
    @Published private(set) var deck: Deck
    // ...
}

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: SwitchControlChallengeApp; View: CardView, ContentView, GameBoardView.
• Protocols: no local protocol declaration in the scanned source.
• Methods: shuffle, getCard, toggle, isMatch, select, reset, randomSymbol, symbolSet.
• Files: SwitchControlChallenge/SwitchControlChallengeApp.swift, SwitchControlChallenge/Views/ContentView.swift, SwitchControlChallenge/Views/GameBoardView.swift, SwitchControlChallenge/Views/CardView.swift, SwitchControlChallenge/Models/Card.swift, SwitchControlChallenge/Models/Deck.swift.

Architecture takeaways

• SwitchControlChallengeApp is the main source-visible entry or composition anchor for this sample.
• Framework work reaches SwiftUI, 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.
• The source does not justify labeling the design protocol-oriented.

Source map

• Official Apple documentation