swift-actor-persistence

Use a Swift actor to wrap your storage logic, since actors guarantee serialized access to mutable state enforced at compile time. Combine an in-memory dictionary cache with atomic JSON file writes for fast reads and durable persistence.

Actors are the recommended approach for new Swift concurrency code because the compiler enforces isolation, eliminating manual synchronization errors. DispatchQueue and NSLock are legacy approaches that rely on developer discipline and can introduce deadlocks or race conditions.

Yes, an @Observable ViewModel can hold a reference to an actor repository and call its methods with await from async functions. The ViewModel updates its published state after awaiting repository operations, keeping the UI reactive.

Atomic writes prevent data corruption if the app crashes mid-write, since the file is written to a temporary location and moved into place only when complete. Without the .atomic option, a crash can leave a partially written, unreadable file.

All actor method calls are asynchronous, so callers must operate in an async context, which adds complexity to synchronous code paths. The pattern also loads data synchronously during init and keeps everything in memory, so it suits small-to-medium local datasets rather than large databases.