Personalizing a Model with On-Device Updates

At a glance

Project structure

Source bundle/
└── PersonalStickers/
    ├── App/
    │   └── AppDelegate.swift
    ├── ViewControllers/
    │   ├── DrawingCanvasViewController.swift
    │   ├── CreateNewStickerViewController.swift
    │   ├── ExampleDrawingViewController.swift
    │   ├── MainCanvasViewController.swift
    │   ├── ProvideExampleDrawingsViewController.swift
    │   └── EmojiCell.swift
    ├── Drawing Data/
    │   ├── ExampleDrawingSet.swift
    │   └── UserDrawing.swift
    └── Model/
        ├── ModelUpdater.swift
        ├── UpdatableDrawingClassifier+ImageConstraint.swift
        └── UpdatableDrawingClassifier+Prediction.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 6 project/configuration file(s) and 11 source declaration(s).

Overall architecture

flowchart LR
    N1["AppDelegate"]
    N2["CreateNewStickerViewController"]
    N3["CoreML APIs"]
    N1 --> N2
    N2 --> N3

Reference code

PersonalStickers/App/AppDelegate.swift:10 — architecture anchor

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

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
    DrawingCanvasViewController o-- DrawingDelegate : delegate
    DrawingCanvasViewController o-- DispatchWorkItem : submitWorkItem
    DrawingCanvasViewController o-- PKCanvasView : canvasView

Ownership evidence

PersonalStickers/App/AppDelegate.swift:12 — 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

PersonalStickers/Model/ModelUpdater.swift:84 — representative execution boundary

            DispatchQueue.main.async { completionHandler() }

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

PersonalStickers/ViewControllers/DrawingCanvasViewController.swift:12 — representative type boundary

protocol DrawingDelegate: AnyObject {
    func didProduce(drawing: UserDrawing, sender: Any?)
}

The source explicitly defines local protocol relationships: ExampleDrawingViewController → DrawingDelegate, MainCanvasViewController → DrawingDelegate, ProvideExampleDrawingsViewController → DrawingDelegate.

Access control

Reference code

PersonalStickers/Drawing Data/ExampleDrawingSet.swift:15 — representative boundary

struct ExampleDrawingSet {
    // ...
    private let requiredDrawingCount = 3
    // ...
}

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: CreateNewStickerViewController, DrawingCanvasViewController, ExampleDrawingViewController, MainCanvasViewController, ProvideExampleDrawingsViewController; Delegate: AppDelegate, DrawingDelegate.
• Protocols: DrawingDelegate.
• Methods: didProduce, viewDidLoad, configureCanvasView, canvasViewDidBeginUsingTool, canvasViewDrawingDidChange, submitDrawing, makeTrainingViewController, cancel.
• Files: PersonalStickers/App/AppDelegate.swift, PersonalStickers/ViewControllers/DrawingCanvasViewController.swift, PersonalStickers/ViewControllers/CreateNewStickerViewController.swift, PersonalStickers/ViewControllers/ExampleDrawingViewController.swift, PersonalStickers/ViewControllers/MainCanvasViewController.swift, PersonalStickers/ViewControllers/ProvideExampleDrawingsViewController.swift.

Architecture takeaways

• AppDelegate is the main source-visible entry or composition anchor for this sample.
• Framework work reaches UIKit, CoreML, CoreImage, PencilKit 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