AutoDefaultsSetting

A Swift macro that automatically generates type-safe UserDefaults setting wrappers for use with the Defaults package.

Overview

AutoDefaultsSetting is a freestanding declaration macro designed to work seamlessly with the Defaults package. It generates boilerplate code for creating DefaultsSetting conforming structures, reducing repetitive code when defining your app's user defaults keys. Instead of manually creating setting structures, the macro generates them for you based on a key, type, and default value.

Note: This macro is designed to be used in conjunction with the Defaults package. Make sure you have it installed in your project.

Installation

Prerequisites

This macro requires the Defaults package. Add both packages to your Package.swift dependencies:

dependencies: [
    .package(url: "https://github.com/sindresorhus/Defaults.git", from: "8.0.0"),
    .package(url: "https://github.com/YOUR_USERNAME/swift-macro-autodefaultssetting.git", from: "1.0.0")
]

Then add them to your target dependencies:

.target(
    name: "YourTarget",
    dependencies: [
        .product(name: "Defaults", package: "Defaults"),
        .product(name: "AutoDefaultsSetting", package: "swift-macro-autodefaultssetting")
    ]
)

Required Protocol Definition

You must include the following DefaultsSetting protocol definition once in your project. This protocol provides the foundation for the generated setting structures:

public import Defaults

public protocol DefaultsSetting {
  associatedtype Value: Defaults.Serializable

  var key: Defaults.Key<Value> { get }
}

extension DefaultsSetting {
  public var value: Value {
    Defaults[key]
  }

  public func set(_ value: Value) {
    Defaults[key] = value
  }

  public func updates(
    initial: Bool = true
  ) -> AsyncStream<Value> {
    Defaults.updates(
      key,
      initial: initial
    )
  }
}

Usage

Basic Example

import AutoDefaultsSetting
import Defaults

// Generate a settings wrapper for a String value
#AutoDefaultsSetting(key: "username", type: String.self, default: "Guest")

// This generates:
// public struct UsernameSetting: DefaultsSetting {
//     public static var shared = Self()
//     public let key = Key<String>("username", default: "Guest")
// }

Using the Generated Setting with Defaults

The generated settings come with convenient methods from the DefaultsSetting protocol:

import Defaults

// Access the generated setting
let setting = UsernameSetting.shared

// Read using the value property
let username = setting.value

// Write using the set method
setting.set("John")

// Or use Defaults directly with the key
Defaults[setting.key] = "Jane"

// Observe changes using Swift concurrency
Task {
    for await newValue in setting.updates() {
        print("Username changed to: \(newValue)")
    }
}

// Or use Combine publisher
Defaults.publisher(setting.key)
    .sink { newValue in
        print("Username changed to: \(newValue)")
    }
    .store(in: &cancellables)

Examples with Different Types

// Boolean setting
#AutoDefaultsSetting(key: "isDarkMode", type: Bool.self, default: false)

// Integer setting
#AutoDefaultsSetting(key: "launchCount", type: Int.self, default: 0)

// Double setting
#AutoDefaultsSetting(key: "volume", type: Double.self, default: 0.5)

// Enum setting (enums must conform to Defaults.Serializable)
enum SortOrder: String, Defaults.Serializable {
    case ascending
    case descending
}
#AutoDefaultsSetting(key: "sortOrder", type: SortOrder.self, default: .ascending)

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.