Organize Your User Interface with a Stack View

At a glance

Project structure

Source bundle/
└── InfoBarStackView/
    ├── StackView.swift
    ├── AppDelegate.swift
    ├── CollectionViewController.swift
    ├── HeaderViewController.swift
    ├── TableViewController.swift
    ├── ViewController.swift
    ├── BaseViewController.swift
    ├── FormViewController.swift
    ├── MainViewController.swift
    ├── OtherViewController.swift
    ├── WindowController.swift
    └── CollectionItem.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 8 project/configuration file(s) and 19 source declaration(s).

Overall architecture

flowchart LR
    N1["AppDelegate"]
    N2["BaseViewController"]
    N3["Cocoa APIs"]
    N1 --> N2
    N2 --> N3

Reference code

InfoBarStackView/AppDelegate.swift:10 — architecture anchor

@NSApplicationMain
class AppDelegate: NSObject, NSApplicationDelegate {
    /*  Pre-load the stack view window controller and its content view controller.
        Used for state restoration and opening its window via the "Show Stack View" button.
    */
    var stackViewWindowController =
        NSStoryboard(name: "Main", bundle: nil).instantiateController(withIdentifier: "WindowController") as? WindowController
}

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 AppKit.

Ownership and state

classDiagram
    StackItemContainer o-- StateValue : state
    StackItemContainer o-- StackItemHeader : header
    StackItemContainer o-- StackItemBody : body
    CollectionViewController o-- NSCollectionView : collection

Ownership evidence

InfoBarStackView/StackView.swift:124 — stored dependency or nearest verified ownership anchor

class StackItemContainer {
    // ...
    var state: NSControl.StateValue
    // ...
}

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.

No source-visible execution, scheduling, or synchronization boundary was found in the indexed source.

@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.

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

InfoBarStackView/StackView.swift:13 — representative type boundary

protocol StackItemHost: AnyObject {
    func disclose(_ stackItem: StackItemContainer)
}

The source explicitly defines local protocol relationships: BaseViewController → StackItemBody, HeaderViewController → StackItemHeader, ViewController → StackItemHost.

Access control

Reference code

InfoBarStackView/CollectionViewController.swift:18 — representative boundary

class CollectionViewController: BaseViewController, NSCollectionViewDataSource, NSCollectionViewDelegate {
    // ...
    private static let collectionItemIdentifier = "CollectionItem"

    // ...
}

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: BaseViewController, CollectionViewController, FormViewController, HeaderViewController, MainViewController; Delegate: AppDelegate; View: CustomStackView, HeaderView.
• Protocols: StackItemHost, StackItemHeader, StackItemBody.
• Methods: disclose, update, show, hide, animateDisclosure, headerTitle, viewDidLoad, collectionView.
• Files: InfoBarStackView/AppDelegate.swift, InfoBarStackView/CollectionViewController.swift, InfoBarStackView/HeaderViewController.swift, InfoBarStackView/TableViewController.swift, InfoBarStackView/ViewController.swift, InfoBarStackView/BaseViewController.swift.

Architecture takeaways

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