Understanding a Dice Roll with Vision and Object Detection

At a glance

Project structure

Source bundle/
├── MLDice/
│   ├── AppDelegate.swift
│   ├── ViewController.swift
│   ├── Utilities/
│   │   ├── ThresholdProvider.swift
│   │   └── GeometryUtilities.swift
│   ├── ViewController+ARSessionHandling.swift
│   ├── ViewController+BoundingBoxes.swift
│   ├── Base.lproj/
│   │   ├── LaunchScreen.storyboard
│   │   └── Main.storyboard
│   └── Info.plist
├── Configuration/
│   └── SampleCode.xcconfig
└── MLDice.xcodeproj/
    ├── .xcodesamplecode.plist
    └── project.pbxproj

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 6 project/configuration file(s) and 4 source declaration(s).

Overall architecture

flowchart LR
    N1["AppDelegate"]
    N2["ViewController"]
    N3["ThresholdProvider"]
    N4["UIKit / Vision APIs"]
    N1 --> N2
    N2 --> N3
    N3 --> N4

Reference code

MLDice/AppDelegate.swift:10 — architecture anchor

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {

    var window: UIWindow?

    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
        // Override point for customization after application launch.
        return true
    }
}

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 Core ML.

Ownership and state

classDiagram
    AppDelegate o-- UIWindow : window
    ViewController *-- DispatchQueue : predictionQueue
    ViewController o-- ARSCNView : sceneView
    ViewController o-- UILabel : infoLabel

Ownership evidence

MLDice/AppDelegate.swift:13 — stored dependency or nearest verified ownership anchor

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {
    // ...
    var window: UIWindow?
    // ...
}

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

MLDice/ViewController+BoundingBoxes.swift:14 — representative execution boundary

        DispatchQueue.main.async {
            self.detectionOverlay = CALayer() // container layer that has all the renderings of the observations
            // ...
        }

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

MLDice/AppDelegate.swift:11 — representative type boundary

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {
    // ...
    var window: UIWindow?
    // ...
}

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

Access control

Reference code

MLDice/Utilities/ThresholdProvider.swift:23 — representative boundary

class ThresholdProvider: MLFeatureProvider {
    /// The actual values to provide as input
    ///
    /// Create ML Defaults are 0.45 for IOU and 0.25 for confidence.
    /// Here the IOU threshold is relaxed a little bit because there are
    /// sometimes multiple overlapping boxes per die.
    /// Technically, relaxing the IOU threshold means
    /// non-maximum-suppression (NMS) becomes stricter (fewer boxes are shown).
    /// The confidence threshold can also be relaxed slightly because
    /// objects look very consistent and are easily detected on a homogeneous
    /// background.
    open var values = [
        "iouThreshold": MLFeatureValue(double: 0.3),
        "confidenceThreshold": MLFeatureValue(double: 0.2)
    ]

    /// The feature names the provider has, per the MLFeatureProvider protocol
    var featureNames: Set<String> {
        return Set(values.keys)
    }

    /// The actual values for the features the provider can provide
    func featureValue(for featureName: String) -> MLFeatureValue? {
        return values[featureName]
    }
}

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: Controller: ViewController; Delegate: AppDelegate; Provider: ThresholdProvider.
• Protocols: no local protocol declaration in the scanned source.
• Methods: application, viewDidLoad, viewDidAppear, viewWillDisappear, bounds, detectionRequestHandler, hasRollEnded, featureValue.
• Files: MLDice/AppDelegate.swift, MLDice/ViewController.swift, MLDice/Utilities/ThresholdProvider.swift.

Architecture takeaways

• AppDelegate is the main source-visible entry or composition anchor for this sample.
• Framework work reaches UIKit, Vision, ARKit, CoreGraphics 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