AppKit: NSViewController, Documents & SwiftUI Interop

NSViewController

class ProfileViewController: NSViewController {
  override func viewDidLoad() {
    super.viewDidLoad()
    // set up view hierarchy
  }
}

// Conceptually analogous to UIViewController's lifecycle,
// adapted to macOS's windowed, mouse/keyboard-driven model

Document-Based Apps

NSDocument provides a framework for document-based apps (like a text editor) -- handling file I/O, undo management, autosave, and multi-window document architecture out of the box.

Bridging to SwiftUI

struct LegacyEditorView: NSViewRepresentable {
  func makeNSView(context: Context) -> LegacyEditor {
    LegacyEditor()
  }
  func updateNSView(_ view: LegacyEditor, context: Context) {}
}

// Wraps an existing AppKit NSView so it can be used inside
// a modern SwiftUI view hierarchy -- common in hybrid codebases

Why Teams Still Reach for AppKit

While SwiftUI has matured significantly, some advanced macOS behaviors -- complex text editing, specific window management, certain performance-critical drawing -- are still more directly and maturely supported through AppKit. Many real-world apps mix both: SwiftUI for newer UI, AppKit for legacy or advanced functionality via interop.

NSApplication: The App Lifecycle

NSApplication is the singleton coordinating the app's main event loop and lifecycle events (launch, termination), with an app delegate object commonly handling key callbacks -- the macOS counterpart to UIApplication on iOS.