WWDC21 Challenge: Large Text Challenge

At a glance

Project structure

Source bundle/
└── LargeTextChallenge/
    ├── LargeTextChallengeApp.swift
    ├── Models/
    │   ├── Scenario.swift
    │   └── Texture.swift
    └── Views/
        ├── IntroView.swift
        ├── ScenarioFeedbackView.swift
        ├── Scenarios/
        │   ├── ExerciseFour.swift
        │   ├── ExerciseThree.swift
        │   ├── ExerciseOne.swift
        │   ├── ExerciseFive.swift
        │   └── ExerciseTwo.swift
        ├── ContentView.swift
        └── Supporting/
            └── ImageShapes.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 4 project/configuration file(s) and 44 source declaration(s).

Overall architecture

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

Reference code

LargeTextChallenge/LargeTextChallengeApp.swift:10 — architecture anchor

@main
struct LargeTextChallengeApp: 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
    Scenario *-- Int : id
    Scenario *-- String : name
    Scenario *-- String : description
    Scenario o-- ScenarioKey : exercise

Ownership evidence

LargeTextChallenge/Models/Scenario.swift:12 — stored dependency or nearest verified ownership anchor

struct Scenario: Hashable, Codable, Identifiable {
    let id: Int
    let name: String
    let description: String
    let exercise: ScenarioKey
    let feedback: [ScenarioFeedback]
}

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.

No source-visible execution, scheduling, or synchronization boundary was found in the indexed source.

@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.

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

LargeTextChallenge/Views/ScenarioFeedbackView.swift:11 — representative type boundary

protocol ScenarioFeedbackProtocol {
    func results() -> [ScenarioFeedbackResult]
}

The source explicitly defines local protocol relationships: ExerciseFiveProperties → ScenarioFeedbackProtocol, ExerciseFourProperties → ScenarioFeedbackProtocol, ExerciseOneProperties → ScenarioFeedbackProtocol, ExerciseThreeProperties → ScenarioFeedbackProtocol, ExerciseTwoProperties → ScenarioFeedbackProtocol.

Access control

Reference code

LargeTextChallenge/Models/Texture.swift:13 — representative boundary

struct Texture: Hashable, Codable, Identifiable {
    let id: Int
    let name: String
    fileprivate let imageName: String
}

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: LargeTextChallengeApp; View: ContentView, ExerciseOneButtonView, ExerciseOneTextView, ExerciseThreeImageView, ExerciseThreeLargeImageView.
• Protocols: ScenarioFeedbackProtocol.
• Methods: results.
• Files: LargeTextChallenge/LargeTextChallengeApp.swift, LargeTextChallenge/Models/Scenario.swift, LargeTextChallenge/Views/IntroView.swift, LargeTextChallenge/Views/ScenarioFeedbackView.swift, LargeTextChallenge/Views/Scenarios/ExerciseFour.swift, LargeTextChallenge/Views/Scenarios/ExerciseThree.swift.

Architecture takeaways

• LargeTextChallengeApp 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.
• Local protocol relationships provide an explicit substitution boundary.

Source map

• Official Apple documentation