KeychainStorageKit

Contains a single property wrapper, @KeychainStorage, for conviently and securely storing sensitive data in the iOS Keychain.

Features

• Simple, declarative syntax similar to @AppStorage
• Minimalistic implementation—just a single file (should you wish to copy-and-paste!)
• Compatible with Swift 6 and low deployment targets

Supported Types

• Basic Types: String, Int, Double, Bool
• Foundation Types: URL, Data
• Custom Types: Any custom type that that conforms to Codable

Installation

You can integrate KeychainStorageKit into your project using Swift Package Manager:

1. In Xcode, select your project in the Project Navigator
2. Go to the Package Dependencies tab
3. Click the + button to add a package dependency
4. In the search bar, enter the repository URL for: https://github.com/maxhumber/KeychainStorageKit

Usage

The syntax of @KeychainStorage is familiar and feels like a close cousin of @AppStorage:

import KeychainStorageKit

func setToken(_ newToken: String) {
    @KeychainStorage("authToken") var token: String?
    token = newToken
}

func getToken() -> String? {
    @KeychainStorage("authToken") var token: String?
    return token
}

func removeToken() {
    @KeychainStorage("authToken") var token: String?
    token = nil
}

Usage within a SwiftUI App

Here's how you might use the @KeychainStorage wrapper in a SwiftUI app:

import KeychainStorageKit
import SwiftUI

// MARK: - API Client
struct FetchClient {
    var fetch: @Sendable () async throws -> String
    
    static let live = FetchClient(
        fetch: {
            @KeychainStorage("token") var token: String?
            let result = "Result from token: [\(token ?? "missing")]" // Use token
            return result
        }
    )
    
    static let preview = FetchClient(
        fetch: {
            try await Task.sleep(for: .seconds(2))
            return "Result for preview [no token]"
        }
    )
}

extension EnvironmentValues {
    @Entry var fetchClient: FetchClient = .live
}

// MARK: - View
struct ContentView: View {
    @Environment(\.fetchClient) var client: FetchClient
    @State var result: String?
    
    var body: some View {
        VStack {
            Text(result ?? "")
            Button("Fetch") {
                Task { await fetch() }
            }
        }
        .task { await tokenRefresh() }
    }
    
    private func fetch() async {
        result = try? await client.fetch()
    }
    
    private func tokenRefresh() async {
        while !Task.isCancelled {
            let newToken = String((0..<5).compactMap { _ in "ABCDEF1234567890".randomElement() })
            print("New token: [\(newToken)]")
            @KeychainStorage("token") var token: String?
            token = newToken // Set token
            try? await Task.sleep(for: .seconds(5))
        }
    }
}

// MARK: - Preview
#Preview {
    ContentView()
        .environment(\.fetchClient, .live) // .environment(\.fetchClient, .preview)
}

// MARK: - Entrypoint
@main
struct KeychainStorageExampleApp: App {
    var body: some Scene {
        WindowGroup {
            ContentView()
        }
    }
}

Tests

Due to Keychain access requirements, the tests for this package must run against a "TestHost" app (following this tutorial). To run the tests:

make test