iOS vs macOS - Developer Cheat Sheet

Critical Framework Differences

AppKit vs UIKit vs SwiftUI

Framework	Platform	Key Classes	Programming Model	Maturity	Event Handling
AppKit	macOS only	NSApplication, NSWindow, NSView, NSViewController, NSMenu	Imperative, verbose, multi-window native	Very Mature (NeXTSTEP roots)	Mouse, Keyboard, Trackpad
UIKit	iOS/Catalyst	UIApplication, UIWindow, UIView, UIViewController	Imperative, touch-first, single-window focus	Mature (iPhoneOS 1)	Touch, Gestures
SwiftUI	Cross-platform	View protocol, WindowGroup, NavigationSplitView	Declarative, platform-adaptive	Maturing (iOS 13/macOS 10.15)	Gesture modifiers, .onHover

Critical: NSWindow is NOT a subclass of NSView (unlike UIWindow/UIView). NS-prefixed classes are NOT direct equivalents of UI-prefixed classes.

Framework Interoperability

// Embed SwiftUI in AppKit
let hostingView = NSHostingView(rootView: MySwiftUIView())
parentView.addSubview(hostingView)

// Embed AppKit in SwiftUI
struct AppKitViewWrapper: NSViewRepresentable {
    func makeNSView(context: Context) -> NSTextField { NSTextField() }
    func updateNSView(_ nsView: NSTextField, context: Context) { }
}

struct AppKitControllerWrapper: NSViewControllerRepresentable {
    func makeNSViewController(context: Context) -> MyViewController { MyViewController() }
    func updateNSViewController(_ nsViewController: MyViewController, context: Context) { }
}

macOS-Specific UI Paradigms

Multi-window environment: Users expect independent, resizable windows
Menu bar centrality: Primary command discovery via persistent menu bar
Precision input: Mouse/trackpad precision vs touch targets
Keyboard shortcuts: Essential for native feel
Window states: Key vs Main window distinction critical

Window Management (macOS-Specific)

NSWindow & NSWindowController

// NSWindow is NOT an NSView subclass
let window = NSWindow(contentRect: rect,
                     styleMask: [.titled, .resizable, .closable, .miniaturizable],
                     backing: .buffered, defer: false)
window.contentView = myRootView

Key NSWindow Properties:

styleMask: Defines appearance and controls (close, minimize, resize buttons)
backing: How content is buffered (.buffered, .retained, .nonretained)
contentView: Root NSView in the window's hierarchy