Building a document-based app with SwiftUI

At a glance

Project structure

Source bundle/
├── WritingApp/
│   ├── WritingApp.swift
│   ├── Views/
│   │   ├── AccessoryView.swift
│   │   ├── StoryView.swift
│   │   └── StorySheet.swift
│   ├── WritingAppDocument.swift
│   ├── Extensions/
│   │   ├── UTType+WritingApp.swift
│   │   └── Color.swift
│   ├── Info.plist
│   └── WritingApp.entitlements
├── Configuration/
│   └── SampleCode.xcconfig
└── WritingApp.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 5 project/configuration file(s) and 6 source declaration(s).

Overall architecture

flowchart LR
    N1["WritingApp"]
    N2["AccessoryView"]
    N3["WritingAppDocument"]
    N4["SwiftUI APIs"]
    N1 --> N2
    N2 --> N3
    N3 --> N4

Reference code

WritingApp/WritingApp.swift:11 — architecture anchor

@main
struct WritingApp: 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
    AccessoryView *-- CGSize : size
    StoryView o-- WritingAppDocument : document
    StoryView *-- Bool : isFocused
    WritingAppDocument *-- String : story

Ownership evidence

WritingApp/Views/AccessoryView.swift:12 — stored dependency or nearest verified ownership anchor

    @Environment(\.horizontalSizeClass) private var horizontal
    @State private var size: CGSize = CGSize()

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

WritingApp/WritingApp.swift:12 — representative type boundary

struct WritingApp: App {
    // ...
}

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

Access control

Reference code

WritingApp/Views/AccessoryView.swift:11 — representative boundary

    @Environment(\.horizontalSizeClass) private var horizontal

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: WritingApp; Document: WritingAppDocument; View: AccessoryView, StoryView.
• Protocols: no local protocol declaration in the scanned source.
• Methods: fileWrapper.
• Files: WritingApp/WritingApp.swift, WritingApp/Views/AccessoryView.swift, WritingApp/Views/StoryView.swift, WritingApp/WritingAppDocument.swift, WritingApp/Views/StorySheet.swift.

Architecture takeaways

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