Swift Actor Persistence

This gives you a generic actor-based repository pattern for thread-safe local persistence in Swift. It wraps an in-memory dictionary cache with file-backed JSON storage, so reads are fast and writes are durable. The actor isolation means no manual locks or dispatch queues, and the compiler enforces thread safety at build time. You get synchronous loading during init to avoid async initialization hell, atomic file writes to prevent corruption on crashes, and it works with any Codable type that has a string ID. Solid choice for offline-first iOS apps or anywhere you need shared mutable state without the usual concurrency footguns. The ViewModel integration example shows how it composes cleanly with SwiftUI's Observable macro.

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last updated: Aug 21, 2026

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Install

$ npx -y skills add affaan-m/ecc --skill swift-actor-persistence --agent claude-code

Installs into .claude/skills of the current project.

Files

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.

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

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