swift-actor-persistence
Thread-safe data persistence in Swift using actors — in-memory cache with file-backed storage, eliminating data races by design. Use when persisting data in Swift and a data race or thread-safety problem needs designing out.
- Kind
- Skill
- Works with
- Claude Code, Codex
- Languages
- Swift
- Source
- affaan-m/ECC @ d3b8a3e90890
- Path
- skills/swift-actor-persistence/SKILL.md
- License
- MIT
- Jobs
- Context management, Guardrails
InstallCopy it from the source repository, or sign in and let the assistant adapt it for your project.
# Swift Actors for Thread-Safe 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.
## When to Activate
- 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
## Core Pattern
### Actor-Based Repository
The actor model guarantees serialized access — no data races, enforced by the compiler.
```swift
public actor LocalRepository<T: Codable & Identifiable> where T.ID == String {
private var cache: [String: T] = [:]
private let fileURL: URL
public init(directory: URL = .documentsDirectory, filename: String = "data.json") {
self.fileURL = directory.appendingPathComponent(filename)
// Synchronous load during init (actor isolation not yet active)
self.cache = Self.loadSynchronously(from: fileURL)
}
// MARK: - Public API
public func save(_ item: T) throws {
cache[item.id] = item
try persistToFile()
}
…