Swift Actor-Based Data Persistence

Thread-safe data storage in Swift using the actor model, which provides compile-time guarantees against data races.

When to Activate

• Building offline-first applications that need thread-safe persistence
• Implementing local caches or data stores in Swift
• Replacing manual synchronization (locks, dispatch queues) with actors
• Integrating persistence with SwiftUI via @Observable view models

Core Pattern

The pattern centers on an actor generic over Codable & Identifiable types that maintains an in-memory dictionary and persists to disk atomically:

actor DataRepository<T: Codable & Identifiable> where T.ID: Hashable & Codable {
    private var items: [T.ID: T] = [:]
    private let fileURL: URL