Creating and Customizing the Touch Bar

At a glance

Project structure

├── Swift/NSTouchBar Catalog/
│   ├── AppDelegate.swift
│   ├── PrimaryViewController.swift
│   ├── WindowController.swift
│   ├── PhotoManager.swift
│   └── *ViewController.swift
└── Objective-C/NSTouchBar Catalog/
    ├── main.m, AppDelegate.{h,m}
    ├── PrimaryViewController.{h,m}
    └── TestViewControllers/**

This is a broad API catalog, not one production feature graph. The language trees should be read as alternatives, not as layers that call each other.

Overall architecture

flowchart LR
    App["Swift app or Objective-C app"] --> Window["WindowController"]
    Window --> Split["Split view"]
    Split --> Primary["PrimaryViewController"]
    Primary --> Plist["Tests.plist"]
    Primary --> Detail["Selected feature storyboard controller"]
    Detail --> TouchBar["NSTouchBar + item delegates"]
    Primary -. binds touchBar .-> Detail

Reference code

Swift/NSTouchBar Catalog/PrimaryViewController.swift:63 — catalog data selects a storyboard and replaces the detail item.

guard let arrangedObjects = contentArray.arrangedObjects as? [AnyObject],
    let testCase = arrangedObjects[tableView.selectedRow] as? [String: String],
    let storyboardName = testCase[TestCaseKey.kind]
    else { return }

viewController = NSStoryboard(name: NSStoryboard.Name(storyboardName), bundle: nil)
    .instantiateInitialController() as! NSViewController

Ownership and state

classDiagram
    WindowController *-- NSWindowController : background window
    PrimaryViewController o-- NSViewController : active detail
    NSViewController *-- NSTouchBar : creates on demand
    NSTouchBar o-- NSTouchBarItem : delegates creation
    PhotoManager *-- Array : photos
    PhotoManager --> PhotoManagerDelegate : weak notification

Ownership evidence

Swift/NSTouchBar Catalog/PhotoManager.swift:11 — the photo catalog is one shared owner with a weak observer.

final class PhotoManager {
    // ...
}

Window and feature controllers own their AppKit objects. The primary controller owns the active detail relationship and binds its touchBar to that controller. PhotoManager.shared owns asynchronously loaded thumbnails and reports completion without retaining its delegate.

Class and protocol design

AppKit delegate conformances are commonly placed in Swift extensions; the Objective-C version keeps public declarations in headers and implementation details in .m class extensions.

Access control

Objective-C/NSTouchBar Catalog/PrimaryViewController.m:10 demonstrates the private class-extension surface for outlets.

Logic ownership and placement

Design patterns

Naming conventions

• Controllers are named after the API variant they demonstrate: ButtonViewController, ScrubberViewController, and PopoverViewController.
• Identifier properties describe the corresponding item (button, buttonBar) and use reverse-DNS raw values.
• Views use visual-role suffixes such as ItemView, BackgroundView, and OverlayView.

Architecture takeaways

• A catalog scales by routing metadata to small, isolated feature controllers.
• Keep touch-bar item construction beside the actions and state it controls.
• Treat the Swift and Objective-C trees as reference alternatives.
• The sample favors framework delegates and target/action; only the photo callback is an app-defined protocol.

Source map

• Official Apple documentation