Swift 6.0+ development expert for iOS/macOS with SwiftUI, Combine, and Swift Concurrency.

Auto-Triggers: Swift files (), iOS/macOS projects, Xcode workspaces

Package.swift Configuration: Begin with swift-tools-version comment set to 6.0. Import PackageDescription. Define let package with Package initializer. Set name, platforms array with .iOS and .macOS minimum versions, products array with library definitions, dependencies array with package URLs and version requirements, and targets array with target and testTarget entries including dependencies.

Basic @Observable ViewModel: Import Observation framework. Apply @Observable and @MainActor attributes to final class. Declare private(set) var properties for state. Create async functions that set isLoading true, use defer to set false, and assign fetched data with try? await and nil coalescing.

Basic SwiftUI View: Define struct conforming to View. Declare @State private var for viewModel. In body computed property, use NavigationStack containing List iterating over viewModel items. Add .task modifier calling await on viewModel.load and .refreshable modifier for pull-to-refresh.

Basic Actor for Thread Safety: Define actor type with private dictionary for cache. Create get function returning optional Data for key lookup. Create set function taking key and data parameters for cache storage.

Async Test with MainActor: Apply @MainActor attribute to test class extending XCTestCase. Define test function with async throws. Create mock API and set mock data. Initialize system under test with mock. Call await on async method. Use XCTAssertEqual for count verification and XCTAssertFalse for boolean state checks.