Drawing content in a group session

At a glance

Project structure

Source bundle/
├── DrawTogether/
│   ├── DrawTogetherApp.swift
│   ├── View/
│   │   ├── CanvasView.swift
│   │   ├── ContentView.swift
│   │   ├── StrokeView.swift
│   │   ├── PhotoPlacementView.swift
│   │   ├── ControlBar.swift
│   │   └── StrokeColorIndicator.swift
│   └── Model/
│       ├── Messages.swift
│       ├── Stroke.swift
│       ├── Canvas.swift
│       └── DrawTogether.swift
└── Configuration/
    └── SampleCode.xcconfig

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 15 source declaration(s).

Overall architecture

flowchart LR
    N1["DrawTogetherApp"]
    N2["ContentView"]
    N3["GroupActivities APIs"]
    N1 --> N2
    N2 --> N3

Reference code

DrawTogether/DrawTogetherApp.swift:10 — architecture anchor

@main
struct DrawTogetherApp: 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 GroupActivities.

Ownership and state

classDiagram
    CanvasView o-- Canvas : canvas
    ContentView *-- Canvas : canvas
    StrokeView o-- Stroke : stroke
    PhotoPlacementView *-- CGPoint : location

Ownership evidence

DrawTogether/View/CanvasView.swift:11 — stored dependency or nearest verified ownership anchor

struct CanvasView: View {
    @ObservedObject var canvas: Canvas
    // ...
}

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.

Class and protocol design

DrawTogether/DrawTogetherApp.swift:11 — representative type boundary

struct DrawTogetherApp: App {
    var body: some Scene {
        WindowGroup {
            ContentView()
        }
    }
}

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

Access control

Reference code

DrawTogether/View/ControlBar.swift:15 — representative boundary

struct ControlBar: View {
    // ...
    @State private var selectedItem: PhotosPickerItem? = nil
    // ...
}

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: DrawTogetherApp; View: CanvasView, ContentView, PhotoPlacementView, StrokeView.
• Protocols: no local protocol declaration in the scanned source.
• Methods: encode, addPointToActiveStroke, finishStroke, finishImagePlacement, reset, startSharing, configureGroupSession, handle.
• Files: DrawTogether/DrawTogetherApp.swift, DrawTogether/View/CanvasView.swift, DrawTogether/View/ContentView.swift, DrawTogether/View/StrokeView.swift, DrawTogether/View/PhotoPlacementView.swift, DrawTogether/Model/Stroke.swift.

Architecture takeaways

• DrawTogetherApp is the main source-visible entry or composition anchor for this sample.
• Framework work reaches SwiftUI, GroupActivities, PhotosUI 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