brdohman/swift-patterns

Project Swift Conventions

Services Must Be Actors

All service types use actor, not class. This is the project standard for thread safety.

actor ItemService: ItemServiceProtocol {
    static let shared = ItemService()
    // ...
}

Typed Throws (Swift 6+)

Use domain-specific typed throws in services. Avoids catching any Error at call sites.

func fetchItems() throws(AppError) -> [Item]

Strict Concurrency

Project targets Swift 6 strict concurrency. All types crossing async boundaries must be Sendable. Use @unchecked Sendable only on mock types in tests.

@Observable Over ObservableObject

ViewModels use @Observable macro (macOS 14+). Never use ObservableObject/@Published. Views own ViewModels with @State private var viewModel = MyViewModel().

No Combine

Use async/await exclusively. No Publisher, sink, or @Published in production code.

Migration Checklist (when touching legacy code)

• Replace ObservableObject + @Published with @Observable
• Replace completion handlers with async throws
• Add Sendable conformance to value types used across tasks
• Replace class services with actor