userdefaults+subscript-1.swift

class SettingsService {

    private enum Keys {
        static let isNotificationsEnabled = "isNotificationsEnabled"
    }

    var isNotificationsEnabled: Bool {
        get {
            let isEnabled = UserDefaults.standard.value(forKey: Keys.isNotificationsEnabled) as? Bool
            return isEnabled ?? true
        }
        set {
            UserDefaults.standard.setValue(newValue, forKey: Keys.isNotificationsEnabled)
        }
    }
}