propertyWrapper

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extension UserDefaults {
    enum Keys {
        static let isFirstLaunch = "isFirstLaunch"
    }
  }

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@propertyWrapper
struct UserDefaultWrapper<T> {
    private let key: String
    private let defaultValue: T

    init(key: String, defaultValue: T) {
        self.key = key
        self.defaultValue = defaultValue
    }

    var wrappedValue: T {
        get {
            UserDefaults.standard.object(forKey: key) as? T ?? defaultValue
        }
        set {
            UserDefaults.standard.set(newValue, forKey: key)
        }
    }
}

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class UserDefaultsManage {
    @UserDefaultWrapper(key: UserDefaults.Keys.isFirstLaunch, defaultValue: false)
    var isFirstLaunch: Bool
}

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class ViewController: UIViewController {
    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view.
        let value = UserDefaultWrapper(key: UserDefaults.Keys.isFirstLaunch, defaultValue: true)
        print(value.wrappedValue)

        print(UserDefaultsManage().isFirstLaunch)
    }
}