Creating custom container views

At a glance

Project structure

Source bundle/
└── DisplayBoardContainer/
    └── DisplayBoardContainer/
        ├── DisplayBoardContainerApp.swift
        ├── DisplayBoardLayout.swift
        ├── HeaderFooterCardView.swift
        ├── CardView.swift
        ├── DisplayBoardBackgroundView.swift
        ├── ContentView.swift
        ├── PinView.swift
        ├── SampleData.swift
        ├── RandomNumberGenerator+Extension.swift
        ├── CardStyle.swift
        ├── DisplayBoard_v1.swift
        └── DisplayBoard_v2.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 3 project/configuration file(s) and 27 source declaration(s).

Overall architecture

flowchart LR
    N1["DisplayBoardContainerApp"]
    N2["ContentView"]
    N3["CardRandomGenerator"]
    N4["SwiftUI APIs"]
    N1 --> N2
    N2 --> N3
    N3 --> N4

Reference code

DisplayBoardContainer/DisplayBoardContainer/DisplayBoardContainerApp.swift:10 — architecture anchor

@main
struct DisplayBoardContainerApp: 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 SwiftUI.

Ownership and state

classDiagram
    DisplayBoardCardLayout o-- Content : content
    DisplayBoardSectionCardLayout o-- Content : content
    DisplayBoardSectionCardLayout *-- UInt64 : sectionSeed
    DisplayBoardSectionCardLayout *-- UInt64 : sectionRandomSeedOffset

Ownership evidence

DisplayBoardContainer/DisplayBoardContainer/DisplayBoardLayout.swift:12 — stored dependency or nearest verified ownership anchor

struct DisplayBoardCardLayout<Content: View>: View {
    @ViewBuilder var content: Content
    // ...
}

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

DisplayBoardContainer/DisplayBoardContainer/DisplayBoardLayout.swift:47 — representative execution boundary

@MainActor

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

DisplayBoardContainer/DisplayBoardContainer/DisplayBoardContainerApp.swift:11 — representative type boundary

@main
struct DisplayBoardContainerApp: App {
    // ...
            ContentView()
    // ...
}

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

Access control

Reference code

DisplayBoardContainer/DisplayBoardContainer/CardView.swift:22 — representative boundary

struct CardView<Content: View>: View {
    // ...
    @State private var defaultRotation: Angle?
    // ...
}

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: DisplayBoardContainerApp; Generator: CardRandomGenerator, DisplayBoardRandomGenerator; View: CardView, CircleAreaView, ContentView, DisplayBoardBackgroundView, DisplayBoardSectionBackgroundView.
• Protocols: no local protocol declaration in the scanned source.
• Methods: makeCache, updateCache, sizeThatFits, placeSubviews, isValidPoint, fill, sample.
• Files: DisplayBoardContainer/DisplayBoardContainer/DisplayBoardContainerApp.swift, DisplayBoardContainer/DisplayBoardContainer/HeaderFooterCardView.swift, DisplayBoardContainer/DisplayBoardContainer/CardView.swift, DisplayBoardContainer/DisplayBoardContainer/DisplayBoardBackgroundView.swift, DisplayBoardContainer/DisplayBoardContainer/ContentView.swift, DisplayBoardContainer/DisplayBoardContainer/PinView.swift.

Architecture takeaways

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