swift-actor-persistence

Patterns for building thread-safe data persistence layers using Swift actors. Combines in-memory caching with file-backed storage, leveraging the actor model to eliminate data races at compile time. The actor model guarantees serialized access — no data races, enforced by the compiler. All calls are automatically async due to actor isolation: - Building a data persistence layer in Swift 5.5+ - Need thread-safe access to shared mutable state - Want to eliminate manual synchronization (locks, DispatchQueues) - Building offline-first apps with local storage - Use Sendable types for all data crossing actor boundaries - Keep the actor's public API minimal — only expose domain operations, not persistence details - Use .atomic writes to prevent data corruption if the app crashes mid-write - Load synchronously in init — async initializers add complexity with minimal benefit for local files - Combine with @Observable ViewModels for reactive UI updates - Using DispatchQueue or NSLock instead of actors for new Swift concurrency code - Exposing the internal cache dictionary to external callers - Making the file URL configurable without validation - Forgetting that all actor method calls are await — callers must handle async context - Using nonisolated to bypass actor isolation (defeats the purpose) - Local data storage in iOS/macOS apps (user data, settings, cached content) -...