Combine publishers!

[sunshinejr]

So now you will be able to run:

extension DefaultsKeys {
    var userColorScheme: DefaultsKey<String> { .init("userColorScheme", defaultValue: "default") }
    var userThemeName: DefaultsKey<String?> { .init("userThemeName") }
    var userLastLoginDate: DefaultsKey<Date?> { .init("userLastLoginDate") }
}

final class Test {

    private var colorSchemeObserver: Cancellable?

    func obserColorScheme() {
        colorSchemeObserver = Defaults.publisher(for: \.colorSchemeObserver)
            .sink { value in
                // 
            }
    }
}