Preference provides property wrapper for UserDefaults and custom Combine publisher that bind a stream for changes.

There are several data types already suppored by default such as Bool, Int, Double, Float, String, URL, Data, Array where Element: PreferenceRepresentable, Dictionary where Key == String, Value: PreferenceRepresentable, Optional where Wrapped: PreferenceRepresentable

Also we have a default implementation of PreferenceRepresentable where Self: RawRepresentable, Self.RawValue: PreferenceRepresentable.

// Use String as key
@Preference("isFlagged") var isFlagged = false

...

extension UserDefaults.FieldKey {
    ...
    
    static let isFlagged: UserDefaults.FieldKey = "isFlagged"
}

// Use UserDefaults.FieldKey as key
@Preference(.isFlagged) var isFlagged = false

enum Fruit: String, PreferenceRepresentable {
    ...
    case apple
}

@Preference("fruit") var fruit = Fruit.apple

@Preference("isFlagged") var isFlagged = false
...

$isFlagged.sink {
    print($0)
}
.store(in: &cancellable)

Add the following dependency to your Package.swift file:

.package(url: "https://github.com/hdtls/swift-preference", from: "1.0.2")

Preference is available under the MIT license. See the LICENSE file for more info.