Xcode Swift Developer

Expert guidance for native Apple platform development with Swift and SwiftUI.

When to Use

• Building macOS menu bar apps
• Creating iOS/macOS widgets (WidgetKit)
• Implementing App Intents and Shortcuts
• SwiftUI component architecture
• Xcode project configuration
• Swift Package Manager setup
• Code signing and entitlements
• App Store / TestFlight preparation

Core Principles

SwiftUI Architecture

• Use MVVM with @Observable (iOS 17+) or ObservableObject
• Prefer composition over inheritance
• Keep views small and focused
• Extract reusable components to separate files

Project Structure (macOS Menu Bar App)

AppName/
├── App/
│   └── AppNameApp.swift          # @main entry point
├── Models/
│   ├── ServiceType.swift         # Enums and data models
│   └── UsageMetrics.swift        # Core data structures
├── Services/
│   ├── ServiceManager.swift      # Business logic
│   ├── KeychainManager.swift     # Secure storage
│   └── APIClient.swift           # Network layer
├── Views/
│   ├── MenuBarView.swift         # Main menu bar content
│   ├── SettingsView.swift        # Preferences window
│   └── Components/               # Reusable UI components
└── Info.plist

AppNameWidget/
├── AppNameWidgetBundle.swift     # Widget bundle entry
├── UsageWidget.swift             # Widget implementation
├── Assets.xcassets/
└── Info.plist

Menu Bar App Pattern

@main
struct AppNameApp: App {
    @NSApplicationDelegateAdaptor(AppDelegate.self) var appDelegate

    var body: some Scene {
        MenuBarExtra("App Name", systemImage: "chart.bar") {
            MenuBarView()
        }
        .menuBarExtraStyle(.window)

        Settings {
            SettingsView()
        }
    }
}

Widget Development

• Use TimelineProvider for data updates
• Keep widget views lightweight
• Support multiple widget families (small, medium, large)
• Use @Environment(\.widgetFamily) for adaptive layouts
• Share data via App Groups

Keychain Best Practices

• Use kSecClassGenericPassword for API keys
• Set kSecAttrAccessible appropriately
• Group related items with kSecAttrService
• Handle errors gracefully (item not found, access denied)

Swift Concurrency

• Use async/await for asynchronous operations
• Mark main-thread-bound code with @MainActor
• Use Task for launching async work from sync contexts
• Prefer AsyncStream for continuous data

Code Signing & Entitlements

Common entitlements for menu bar apps:

• com.apple.security.app-sandbox
• com.apple.security.network.client
• com.apple.security.keychain-access-groups
• com.apple.security.application-groups (for widget data sharing)

SwiftLint Configuration

disabled_rules:
  - line_length
  - trailing_whitespace

opt_in_rules:
  - empty_count
  - closure_spacing
  - force_unwrapping

excluded:
  - .build
  - .swiftpm

Common Patterns

API Client

actor APIClient {
    private let session = URLSession.shared
    private let baseURL: URL

    func fetch<T: Decodable>(_ endpoint: String) async throws -> T {
        let url = baseURL.appendingPathComponent(endpoint)
        let (data, response) = try await session.data(from: url)
        guard let httpResponse = response as? HTTPURLResponse,
              (200...299).contains(httpResponse.statusCode) else {
            throw APIError.invalidResponse
        }
        return try JSONDecoder().decode(T.self, from: data)
    }
}

Shared Data Store (App Groups)

final class SharedDataStore {
    static let shared = SharedDataStore()

    private let defaults: UserDefaults

    init() {
        defaults = UserDefaults(suiteName: "group.com.company.appname")!
    }

    var usageData: UsageData? {
        get {
            guard let data = defaults.data(forKey: "usageData") else { return nil }
            return try? JSONDecoder().decode(UsageData.self, from: data)
        }
        set {
            let data = try? JSONEncoder().encode(newValue)
            defaults.set(data, forKey: "usageData")
        }
    }
}

File Naming Conventions

• Views: *View.swift (e.g., SettingsView.swift)
• Models: Descriptive nouns (e.g., UsageMetrics.swift)
• Services: *Manager.swift or *Service.swift
• Extensions: Type+Extension.swift
• Protocols: *Protocol.swift or *able.swift

Testing

• Use XCTest for unit tests
• Test business logic in Services
• Use @testable import for internal access
• Mock network with URLProtocol
• Snapshot test SwiftUI views with swift-snapshot-testing

Build Configuration

Debug vs Release

• Use #if DEBUG for debug-only code
• Configure schemes for different environments
• Use .xcconfig files for build settings
• Keep secrets out of source (use Keychain or secure config)