swift-observable-user-defaults

This library enables us to observe userDefaults easily. It can be managed in Package.swift or Xcode project.

Usage

In order to observe userDefaults, we have to define properties with @UserDefaultsEntry macro in an extension of ObservableUserDefaults.

import ObservableUserDefaults
import ObservableUserDefaultsMacros

extension ObservableUserDefaults {
    // If no argument is passed, the property name `count` is used as a userDefaults key name.
    @UserDefaultsEntry var count = 0

    // If a string is passed, it is used as a userDefaults key name.
    @UserDefaultsEntry("namedTitle") var title: String?
}

A view model is implemented like the following code:

import ObservableUserDefaults
import ObservableUserDefaultsMacros

// Attach `@ObservableWithUserDefaults` to an observed class, instead of `@Observation`.
// Note: APIs in Observation like `@ObservationTracked` and `@ObservationIgnored` still can be used.
@ObservableWithUserDefaults
@MainActor
final class ContentViewModel {
    // Attach `@UserDefaultsTracked` to a variable to track with userDefaults.
    @UserDefaultsTracked(\.count) var count: Int
    @UserDefaultsTracked(\.title) var title: String?

    // Attach `@ObservedUserDefaults` to a variable with type `ObservableUserDefaults`.
    @ObservedUserDefaults
    var observableUserDefaults: ObservableUserDefaults = .standard
}

If we want to observe a custom type with saving userDefaults, it is enough making the type conform to UserDefaultsValueConvertible protocol, like the following code:

extension CustomString: UserDefaultsValueConvertible {
    init(userDefaultsValue: String) {
        self = CustomString(userDefaultsValue)
    }

    var userDefaultsValue: String {
        self.string
    }
}

extension ObservableUserDefaults {
    @UserDefaultsEntry var customString = CustomString("")
}

Quick start

Make sure that xcodegen has been installed, and run the following commands.

$ cd Example
$ xcodegen
$ open ObservableUserDefaultsExample.xcodeproj

You can run the example app by Xcode.

License

This library is released under the MIT license. See LICENSE for details.

TODO

• Create unit tests
• Add documentation comments
• Implement cancellation of observation tasks