WWDC21 Challenge: Framework Freestyle

At a glance

Project structure

Source bundle/
└── FrameworkFreestyle-Challenge/
    ├── ViewController.swift  # ViewController
    ├── AppDelegate.swift  # AppDelegate
    └── Array+Random.swift

Structure observations

• The runtime boundary is UIApplicationDelegate + UIViewController; the tree is pruned to lifecycle, state, framework, rendering, and ECS files.
• The source is Swift; its compact size does not erase any explicit owner shown below.

Overall architecture

flowchart LR
    AppDelegate_1["AppDelegate"]
    UIApplicationDelegate___UIViewController_2["UIApplicationDelegate + UIViewController"]
    ViewController_3["ViewController"]
    RealityKit_entity_graph_4["RealityKit entity graph"]
    ARView_scene_5["ARView scene"]
    AppDelegate_1 --> UIApplicationDelegate___UIViewController_2
    UIApplicationDelegate___UIViewController_2 --> ViewController_3
    ViewController_3 --> RealityKit_entity_graph_4
    RealityKit_entity_graph_4 --> ARView_scene_5

Reference code

FrameworkFreestyle-Challenge/AppDelegate.swift:10 — executable or app-lifecycle anchor.

class AppDelegate: UIResponder, UIApplicationDelegate {

    var window: UIWindow?
}

The diagram is a responsibility flow, not a claim that every adjacent node directly calls the next. It separates lifecycle, presentation, stable state, framework/session work, and the RealityKit entity graph.

Ownership and state

classDiagram
    ViewController --> Face : faceAnchor
    ViewController --> ARView : arView
    ViewController o-- UIButton : button
    ViewController --> RPScreenRecorder : recorder

Ownership evidence

FrameworkFreestyle-Challenge/ViewController.swift:28 — representative stored state or nearest verified lifecycle anchor.

    var faceAnchor: Experience.Face?
    
    // MARK: - Constants -
    
    /// The number of times the timer gets called before displaying image. This adds a delay for the
    /// question mark to spin before the frameworks start displaying.
    let maxTimerCount: Int = 45

Ownership is intentionally narrow: environment, bindings, observed objects, weak links, and delegate callbacks do not prove lifetime ownership. Initialized stored services and wrapper-managed state do; entities added inside a RealityKit content closure belong to that entity graph.

Class and protocol design

The reviewed source defines no local substitution protocol. Its App, View, delegate, renderer, ARKit, and RealityKit conformances are framework-facing contracts, so this document does not label the whole app protocol-oriented.

Access control

No reviewed Swift access example uses fileprivate, private(set), public, open; declarations without a modifier are internal.

Reference code

FrameworkFreestyle-Challenge/ViewController.swift:110 — representative visibility boundary.

    private func startRecording() {
        // ...
    }

Logic ownership and placement

Design patterns

Naming conventions

• Role suffixes are evidence, not decoration: Controller: ViewController.
• Protocols: no app-defined protocol in the reviewed source.
• Commands use verb-led methods: viewDidLoad, viewDidAppear, setupMaterials, toggleRecording, startRecording, stopRecording, handleImageAnimationsSequence, createUnlitMaterialWithTexture.
• Files and folders use primary-type or responsibility names such as Views, Models, Rendering, Components, Systems, Packages, or feature names where those boundaries exist.

Architecture takeaways

• Treat AppDelegate as the owner of executable or scene lifecycle, not automatically as the owner of every entity created later.
• Keep view/controller input near presentation, but move sessions, reconstruction, capture, rendering, shared game state, or documents into stable owners when their lifetime exceeds one callback or render pass.
• The compact source does not justify repository, coordinator, or protocol layers beyond boundaries the sample actually declares.

Source map

• Official Apple documentation