userdefaults+subscript-4.swift

enum AppTheme: Int {
    case light
    case dark
}

class SettingsService {

    var appTheme: AppTheme {
        get {
            if let rawValue: AppTheme.RawValue = UserDefaults.standard[#function], let theme = AppTheme(rawValue: rawValue) {
                return theme
            }
            return .light
        }
        set {
            UserDefaults.standard[#function] = newValue.rawValue
        }
    }
}