Swift 4 JSONDecoder 复杂数据丢失键

Question

我已经为这个问题苦苦挣扎了一天多了，我不确定为什么当我在我的结构中明确定义密钥时，我总是收到丢失密钥错误。非常感谢您的帮助。请帮助消除我对如何解码 JSON.

中的嵌套类型的困惑

我正在尝试解析以下 JSON 响应，但当我运行我的应用程序时，我不断收到“缺少密钥”错误消息。以下是我从该服务返回的消息。

这是 JSON 回复

{
    UserInfo =     {
        ApplicationArea =         {
            CreationDateTime = "2018-02-11 21:34:40.646000";
            MfgCode = PSUN;
            Sender = DM;
        };
        ServiceStatus =         {
            StatusCode = 0;
            StatusDescription = Success;
            System = "Product Info";
        };
        UserInfoDataArea =         {
            Email = "john@example.com";
            Locale = "en_US";
            UserId = 3;
            UserName = jdoe;
        };
    };
}

这是错误

    Missing Key: applicationArea 
Debug description: No value associated with key applicationArea ("ApplicationArea").

下面是我获取请求和解码响应的结构代码。

    struct UserInfo:Codable {

        struct ApplicationArea:Codable {
            let creationDateTime: String
            let mfgCode: String
            let sender: String

            private enum CodingKeys: String, CodingKey {
                case creationDateTime = "CreationDateTime"
                case mfgCode = "MfgCode"
                case sender = "Sender"
            }
        }
        let applicationArea: ApplicationArea

        enum CodingKeys: String, CodingKey {
            case applicationArea = "ApplicationArea"
        }    
    }

创建请求的代码

let apiMethod = HTTPMethod.post

Alamofire.request(
    loginURL!,
    method: apiMethod,
    parameters: params,
    encoding: URLEncoding.default,
    headers: header)
    .responseJSON { (response) -> Void in

        switch response.result {
        case .success:

            print(response.result.value)

            let result = response.data
            do {
                let decoder = JSONDecoder()
                let userDetails = try decoder.decode(UserInfo.self, from: result!)
                    print("Response \(userDetails)")
            } catch DecodingError.keyNotFound(let key, let context) {
                print("Missing Key: \(key)")
                print("Debug description: \(context.debugDescription)")
            } catch {
                print("Error \(error.localizedDescription)")
            }

        case .failure(let error):
            print("Error \(error)")
        }
}

Answer 1

您犯了一个很常见的错误：您忽略了根对象，即包含 UserInfo 键的最外层字典。

创建一个Root结构

struct Root: Decodable {
    let userInfo : UserInfo

    enum CodingKeys: String, CodingKey { case userInfo = "UserInfo" }
}

并解码

let root = try decoder.decode(Root.self, from: result!)
let userDetails = root.userInfo

Swift 4 JSONDecoder 复杂数据丢失键

Swift 4 JSONDecoder Complex Data Missing Key

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swift4

codable