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SwiftPersistence

A protocol-oriented persistence abstraction layer for Swift

Features

• Protocol-Oriented - All persistence operations defined as abstract protocols for DI and testability
• KeyValueStore - Type-safe UserDefaults abstraction (Codable support)
• SecureStore - Safe Keychain wrapper (API key and credential protection)
• DocumentStore - File-based CRUD (individual JSON files, atomic writes)
• RegistryStore - Single JSON file registry pattern
• KeyResolver - Multi-source fallback resolution: Info.plist → Keychain → UserDefaults
• InMemory Test Doubles - Bundled InMemory implementations for all protocols

Installation

// Package.swift
dependencies: [
    .package(url: "https://github.com/no-problem-dev/swift-persistence.git", .upToNextMajor(from: "1.0.0"))
]

Module Structure

Import only the modules you need:

Quick Start

Key-Value Store (UserDefaults Abstraction)

import PersistenceUserDefaults

let store = UserDefaultsKeyValueStore()

// Save and retrieve Codable values
try await store.setValue("dark", forKey: "theme")
let theme: String? = try await store.string(forKey: "theme")

// Custom types supported
struct UserPrefs: Codable, Sendable {
    var fontSize: Int
    var language: String
}
try await store.setValue(UserPrefs(fontSize: 14, language: "en"), forKey: "prefs")
let prefs: UserPrefs? = try await store.value(forKey: "prefs", type: UserPrefs.self)

Secure Store (Keychain Abstraction)

import PersistenceKeychain

let secrets = KeychainSecureStore(service: "com.example.myapp")

// Securely store API keys
try await secrets.setString("sk-abc123...", forKey: "api_key")
let key = try await secrets.getString(forKey: "api_key")

Document Store (File-based CRUD)

import PersistenceFileSystem

struct Note: Codable, Identifiable, Sendable {
    let id: UUID
    var title: String
    var body: String
}

let store = try FileSystemDocumentStore<Note>(
    directory: documentsURL.appendingPathComponent("notes")
)

// CRUD operations
let note = Note(id: UUID(), title: "Memo", body: "Content")
try await store.save(note)
let all = try await store.loadAll()
try await store.delete(id: note.id)

Registry Store (Single JSON Registry)

import PersistenceFileSystem

struct CacheEntry: Codable, Sendable {
    let version: String
    let downloadedAt: Date
}

let registry = FileSystemRegistryStore<CacheEntry>(
    directory: cacheURL,
    filename: "registry.json"
)

var entries = await registry.load()
entries["model-v1"] = CacheEntry(version: "1.0", downloadedAt: Date())
try await registry.save(entries)

Multi-Source Fallback Resolution

import PersistenceCore
import PersistenceKeychain
import PersistenceUserDefaults

let resolver = ChainedKeyResolver(
    secureStore: KeychainSecureStore(service: "com.example.myapp"),
    keyValueStore: UserDefaultsKeyValueStore(),
    keyMapping: [
        "API_KEY": .init(secure: "api_key", keyValue: "api_key"),
    ]
)

// Searches in order: Info.plist → Keychain → UserDefaults
let apiKey = await resolver.resolve("API_KEY")

InMemory Test Doubles

import PersistenceTesting

// Inject via DI in tests
let mockStore = InMemoryKeyValueStore()
let mockSecrets = InMemorySecureStore()
let mockDocs = InMemoryDocumentStore<Note>()

let settings = AppSettings(
    preferences: mockStore,
    secrets: mockSecrets,
    keyResolver: InMemoryKeyResolver(["API_KEY": "test-key"])
)

Architecture

2-layer architecture for separation of concerns:

Layer 0: PersistenceCore           Protocols + error types (no external dependencies)
Layer 1: PersistenceUserDefaults   UserDefaults concrete implementation
         PersistenceKeychain       Keychain concrete implementation
         PersistenceFileSystem     File system concrete implementation
         PersistenceTesting        InMemory test doubles

Requirements

• iOS 17.0+ / macOS 14.0+
• Swift 6.2+
• Xcode 16.0+

License

MIT License - See LICENSE for details

Links

• Report Issues
• Discussions