Adding menus and shortcuts to the menu bar and user interface

At a glance

Project structure

Menus/
├── AppDelegate.swift
├── SceneDelegate.swift
├── MenuController.swift
├── PrimaryViewController.swift
├── PrimaryViewController+Table.swift
├── PrimaryViewController+Toolbar.swift
├── DetailViewController.swift
├── TableItem.swift
└── Base.lproj/Main.storyboard

Structure observations

• MenuController constructs command values; command targets remain on responders such as AppDelegate and the primary controller.
• Primary controller extensions separate table mechanics and Catalyst-only toolbar integration without splitting state ownership.
• Detail-to-primary mutations travel through a weak protocol delegate.

Overall architecture

flowchart LR
    App["AppDelegate"] --> Builder["UIMenuBuilder"]
    App --> Factory["MenuController"]
    Factory --> Menus["UIMenu and UIKeyCommand tree"]
    Menus -. selectors via responder chain .-> Primary["PrimaryViewController"]
    Menus -. app-wide selectors .-> App
    Scene["SceneDelegate"] --> Split["UISplitViewController"]
    Split --> Primary
    Split --> Detail["DetailViewController"]
    Primary -. weak DetailItemDelegate .-> Detail
    Primary --> Toolbar["Catalyst NSToolbar extension"]

Reference code

Menus/AppDelegate.swift:37 — application-level menu construction delegates the command tree to MenuController and keeps validation state in AppDelegate.

override func buildMenu(with builder: UIMenuBuilder) {
    if builder.system == .main {
        menuController = MenuController(with: builder)
        fontMenuStyleStates.insert(MenuController.FontStyle.plain.rawValue)
    }
}

override func validate(_ command: UICommand) {
    if let styles = command.propertyList as? [String: String],
       let style = styles[MenuController.CommandPListKeys.StylesIdentifierKey] {
        command.state = fontMenuStyleStates.contains(style) ? .on : .off
    }
}

Interpretation

Menu definitions and effects are intentionally separated. The builder installs commands with selectors and property-list payloads; UIKit resolves selectors through AppDelegate or the current responder, while validation projects current state back onto commands.

Ownership and state

classDiagram
    AppDelegate *-- MenuController : retains built menu helper
    AppDelegate *-- Set~String~ : owns style state
    UISplitViewController *-- PrimaryViewController : storyboard child
    UISplitViewController *-- DetailViewController : storyboard child
    PrimaryViewController *-- AnyModelItem : stores table items
    PrimaryViewController o-- DetailViewController : lazy lookup
    DetailViewController o-- DetailItemDelegate : weak
    DetailViewController *-- NSKeyValueObservation : retains preferences token
    PrimaryViewController o-- NSToolbarItem : remembers installed items

Ownership evidence

Menus/PrimaryViewController.swift:16 — the primary owns item state and lazily resolves the storyboard-owned detail, then installs itself as weak delegate.

var tableItems = [AnyModelItem]()

lazy var detailViewController: DetailViewController = {
    var result = DetailViewController()
    if let navigation = splitViewController?.viewControllers[1] as? UINavigationController,
       let detail = navigation.topViewController as? DetailViewController {
        result = detail
        result.detailItemDelegate = self
    }
    return result
}()

Class and protocol design

Access control

Reference code

Menus/DetailViewController.swift:20 — the app-defined collaboration is target-local, and the stored delegate is weak.

protocol DetailItemDelegate: NSObjectProtocol {
    func performCutAction()
    func performCopyAction()
    func performPasteAction()
    func performDeleteAction()
    func didUpdateItem(_ item: AnyModelItem)
}

weak var detailItemDelegate: DetailItemDelegate?

Logic ownership and placement

Design patterns

Naming conventions

• MenuController is a construction helper, while action methods end in Action and match selectors.
• Nested enums (Cities, Tools, FontStyle, Arrows) model finite menu groups; CommandPListKeys names payload keys.
• +Table and +Toolbar filenames identify extensions of the same owner.
• Toolbar identifiers use ...ID; Boolean availability is expressed through responder validation rather than stored is... flags.

Architecture takeaways

• Separate menu topology from command effects, then let selectors and responder routing connect them.
• Validate commands from the same owner that holds their state.
• Compile platform-specific integrations out of unsupported targets and keep them in focused extensions.
• Use weak delegates when a detail screen edits data owned by its primary/list screen.

Source map

• Official Apple documentation