Question

当传入的JSON与数据类型不匹配时，JSONDecoder.decode方法不会引发错误。

我有一个像这样的数据模型，它将JSON映射到用户个人资料：

struct DrivetimeUserProfile: Codable {

    var driverId: String?
    var name: String?
    var email: String?
    var phoneNumber: String?
    var city: String?
    var state: String?
    var experience: Int?

    private enum CodingKeys: String, CodingKey {

        case driverId = "driver_id"
        case name = "name"
        case email = "email"
        case phoneNumber = "phone"
        case city = "city"
        case state = "state"
        case experience = "experience"

    }
}

如果用户名或密码不正确，服务器将返回类似\"Failure\":\"Enter correct username and password.\"的JSON。不会映射到用户配置文件数据模型和JSONDecoder（）。decode不会引发错误

这是完整的实现：

func loginUser(from url: URL, with username: String, and password: String, completionHandler: @escaping (DrivetimeUserProfile?, DrivetimeAPIError.LoginError?) -> Void) {

        var request = URLRequest(url: url)
        request.httpMethod = "POST"
        request.cachePolicy = cachePolicy
        request.setValue("application/x-www-form-urlencoded", forHTTPHeaderField: "Content-Type")
        let query = "email=\(username)&password=\(password)"
        request.httpBody = query.data(using: .utf8)

        let task = session.dataTask(with: request) { (data, response, error) in

            guard let data = data else {
                completionHandler(nil, .EmptyData)
                return
            }

            do {
                let userProfile = try JSONDecoder().decode(DrivetimeUserProfile.self, from: data)
                self.userProfile = userProfile

                completionHandler(userProfile, nil)

            } catch (let error) {

                completionHandler(nil, .CannotDecodeJson)
            }
        }
        task.resume()
    }

我需要此完成处理程序来捕获引发的错误，以便可以在我的视图控制器中向用户警告错误是什么。请指教

谢谢

Answer 1

如果不加考虑地将所有struct成员声明为可选的，那就是巨大的缺点。

如果该键不存在于结构中，则所有成员均设置为nil，并且不会引发错误。

当JSON与数据结构不匹配时，JSONDecoder不会抛出

1 个答案: