Composing custom layouts with SwiftUI

At a glance

Project structure

Source bundle/
└── CustomLayoutSample/
    ├── CustomLayoutSampleApp.swift
    ├── Views/
    │   ├── ContentView.swift
    │   ├── ButtonStack.swift
    │   ├── Avatar.swift
    │   ├── Leaderboard.swift
    │   ├── Podium.swift
    │   └── Profile.swift
    ├── Model/
    │   ├── Model.swift
    │   └── Pet.swift
    └── Layouts/
        ├── MyEqualWidthVStack.swift
        ├── MyRadialLayout.swift
        └── MyEqualWidthHStack.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 4 project/configuration file(s) and 15 source declaration(s).

Overall architecture

flowchart LR
    N1["CustomLayoutSampleApp"]
    N2["ContentView"]
    N3["Model"]
    N4["SwiftUI APIs"]
    N1 --> N2
    N2 --> N3
    N3 --> N4

Reference code

CustomLayoutSample/CustomLayoutSampleApp.swift:18 — architecture anchor

@main
struct CustomLayoutSampleApp: App {
    // ...
}

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
    CustomLayoutSampleApp *-- Model : model
    Model *-- Array : pets
    Model *-- Model : startData
    Buttons o-- Model : model

Ownership evidence

CustomLayoutSample/CustomLayoutSampleApp.swift:21 — stored dependency or nearest verified ownership anchor

@main
struct CustomLayoutSampleApp: App {
    // ...
    @StateObject private var model: Model = Model.startData
    // ...
}

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

CustomLayoutSample/CustomLayoutSampleApp.swift:19 — representative type boundary

struct CustomLayoutSampleApp: App {
    // ...
}

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

Access control

Reference code

CustomLayoutSample/CustomLayoutSampleApp.swift:21 — representative boundary

@main
struct CustomLayoutSampleApp: App {
    // ...
    @StateObject private var model: Model = Model.startData
    // ...
}

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: CustomLayoutSampleApp; Model: Model; View: ContentView.
• Protocols: no local protocol declaration in the scanned source.
• Methods: rank, sizeThatFits, placeSubviews, makeCache, maxSize, spacing, getOffset, residual.
• Files: CustomLayoutSample/CustomLayoutSampleApp.swift, CustomLayoutSample/Views/ContentView.swift, CustomLayoutSample/Model/Model.swift, CustomLayoutSample/Views/ButtonStack.swift, CustomLayoutSample/Layouts/MyEqualWidthVStack.swift, CustomLayoutSample/Layouts/MyRadialLayout.swift.

Architecture takeaways

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