SWIFT: 尝试解码 JSON ，它 returns nil

Question

当你尝试调用 .decode() 来解码结构时，它 returns nil.Can 有人帮助我吗？

我的应用从 JSON 数据返回空值，从这行代码：

   let newPosData = try JSONDecoder().decode(NewPosDataBase.self, from: responseData)

完整代码如下：

func getNewLFNREXT(invnr: String, completionHandler: @escaping (String, Bool, NewPosDataBase?) -> Void) {
        let headers: HTTPHeaders = [
            .authorization(username: UserCredentials.shared.username, password: UserCredentials.shared.password),
            .accept("application/json")
        ]
        
        let url:String = Config.middleware + Config.url + "/mobile/lfnrext?invnr=\(invnr)"
        AF.request(url, method: .get, parameters: [:], headers: headers).responseJSON { response in
            if response.response?.statusCode == 200 {
                
                do {
                    guard let responseData = response.data else {
                        completionHandler(errorMessage, false, nil )
                        return
                    }
                    
                    let newPosData = try JSONDecoder().decode(NewPosDataBase.self, from: responseData)
                    
                    print( newPosData.newPosData?.newLfnrext)
                    completionHandler("", true, newPosData)
                    
                } catch {
                    completionHandler(errorMessage, false , nil )
                }
                
            }else {
                let message = self.getErrorMessageFrom(data: response.data, defaultErrorMessage: errorKeineDaten)
                completionHandler(message, false, nil)
            }
        }
        
    }

Answer 1

如果键的名称与 Codable 类型的属性名称不同，您需要添加 enum CodingKeys。

所以，你的模型应该是这样的，

class NewPosDataBase: Codable {
    enum CodingKeys: String, CodingKey {
        case newPosData = "NEW_POS_DATA"
    }
    //rest of the code...
}

class NewPosData: Codable {
    enum CodingKeys: String, CodingKey {
        case newLfnrext = "NEW_LFNREXT"
        case aktuellerZahler = "AKTUELLER_ZAHLER"
        case gpsStd = "GPS_STD"
    }
    //rest of the code...
}

注意：无需在模型中提供任何 init 实现，除非您出于任何特定目的需要它们。

SWIFT: 尝试解码 JSON ，它 returns nil

SWIFT: Trying to decode JSON ,it returns nil

json

swift

codable