在iOS Swift中使用codable解析嵌套的json响应数据？

我试图用swift 4中的可解码格式解析json数据。它打印零值。我找不到这是什么问题

以下是模型类：

public struct TaskID: Decodable {

let embedded: Embedded?
let count: Int?

enum CodingKeys: String, CodingKey {
    case count = "count"
    case embedded = "_embedded"
  }
}

 public struct Embedded: Decodable {


let task: [Task]?
enum CodingKeys: String, CodingKey {
       case task = "task"
   }

 }

public struct Task : Decodable {

let id : String?
let name: String?
let assignee: String?
let created: String?
let processDefinitionId: String?
enum CodingKeys: String, CodingKey {
    case id = "id"
    case name = "name"
    case assignee = "assignee"
    case created = "created"
    case processDefinitionId = "processDefinitionId"


 }

}

以下是json：

{
"_links": {
    "self": {
        "href": "/task"
    }
},
"_embedded": {

    "task": [
        {
            "_links": {
                "assignee": {
                    "href": "/user/demo"
                },
                "execution": {
                    "href": "/execution/1b64cf75-0616-11ea-8860-120ef5ab2c25"
                },
                "identityLink": {
                    "href": "/task/1b64f688-0616-11ea-8860-120ef5ab2c25/identity-links"
                },
                "processDefinition": {
                    "href": "/process-definition/quickEvaluation:1:129ce2b1-0616-11ea-8860-120ef5ab2c25"
                },
                "processInstance": {
                    "href": "/process-instance/1b64cf75-0616-11ea-8860-120ef5ab2c25"
                },
                "self": {
                    "href": "/task/1b64f688-0616-11ea-8860-120ef5ab2c25"
                }
            },
            "_embedded": {
                "variable": []
            },
            "id": "1b64f688-0616-11ea-8860-120ef5ab2c25",
            "name": "Quick Evaluation",
            "assignee": "demo",
            "created": "2019-11-13T13:04:20.687+0000",
            "due": null,
            "followUp": null,
            "delegationState": null,
            "description": null,
            "executionId": "1b64cf75-0616-11ea-8860-120ef5ab2c25",
            "owner": null,
            "parentTaskId": null,
            "priority": 50,
            "processDefinitionId": "quickEvaluation:1:129ce2b1-0616-11ea-8860-120ef5ab2c25",
            "processInstanceId": "1b64cf75-0616-11ea-8860-120ef5ab2c25",
            "taskDefinitionKey": "QuickEvaluation",
            "caseExecutionId": null,
            "caseInstanceId": null,
            "caseDefinitionId": null,
            "suspended": false,
            "formKey": "a8apps:suryoday:gng:v0.1.0:kycUpload",
            "tenantId": null
        },
        {
            "_links": {
                "assignee": {
                    "href": "/user/demo"
                },
                "execution": {
                    "href": "/execution/412a03b7-06ae-11ea-8860-120ef5ab2c25"
                },
                "identityLink": {
                    "href": "/task/412a2aca-06ae-11ea-8860-120ef5ab2c25/identity-links"
                },
                "processDefinition": {
                    "href": "/process-definition/quickEvaluation:1:129ce2b1-0616-11ea-8860-120ef5ab2c25"
                },
                "processInstance": {
                    "href": "/process-instance/412a03b7-06ae-11ea-8860-120ef5ab2c25"
                },
                "self": {
                    "href": "/task/412a2aca-06ae-11ea-8860-120ef5ab2c25"
                }
            },
            "_embedded": {
                "variable": [
                    {
                        "_links": {
                            "self": {
                                "href": "/process-instance/412a03b7-06ae-11ea-8860-120ef5ab2c25/variables/loanAmount"
                            }
                        },
                        "_embedded": null,
                        "name": "loanAmount",
                        "value": "650000",
                        "type": "String",
                        "valueInfo": {}
                    },
                    {
                        "_links": {
                            "self": {
                                "href": "/process-instance/412a03b7-06ae-11ea-8860-120ef5ab2c25/variables/firstName"
                            }
                        },
                        "_embedded": null,
                        "name": "firstName",
                        "value": "Kamesh",
                        "type": "String",
                        "valueInfo": {}
                    }
                ]
            },
            "id": "412a2aca-06ae-11ea-8860-120ef5ab2c25",
            "name": "Quick Evaluation",
            "assignee": "demo",
            "created": "2019-11-14T07:13:27.558+0000",
            "due": null,
            "followUp": null,
            "delegationState": null,
            "description": null,
            "executionId": "412a03b7-06ae-11ea-8860-120ef5ab2c25",
            "owner": null,
            "parentTaskId": null,
            "priority": 50,
            "processDefinitionId": "quickEvaluation:1:129ce2b1-0616-11ea-8860-120ef5ab2c25",
            "processInstanceId": "412a03b7-06ae-11ea-8860-120ef5ab2c25",
            "taskDefinitionKey": "QuickEvaluation",
            "caseExecutionId": null,
            "caseInstanceId": null,
            "caseDefinitionId": null,
            "suspended": false,
            "formKey": "a8apps:suryoday:gng:v0.1.0:kycUpload",
            "tenantId": null
        }

    ]
},
"count": 13
}

这是您的请求：

 // MARK: - URLRequestConvertible
func asURLRequest() throws -> URLRequest {
    let url = try K.ProductionServer.baseURL.asURL()

    var urlRequest = URLRequest(url: url.appendingPathComponent(path))
    print(urlRequest)
    // HTTP Method
    urlRequest.httpMethod = method.rawValue

    let authToken = UserDefaults.standard.string(forKey: "authToken")
    let bearerToken: String = "Bearer " + (authToken ?? "")
    print("baearer token::\(bearerToken)")

    // Common Headers
    urlRequest.setValue(ContentType.json.rawValue, forHTTPHeaderField: HTTPHeaderField.acceptType.rawValue)
    urlRequest.setValue(ContentType.json.rawValue, forHTTPHeaderField: HTTPHeaderField.contentType.rawValue)
    urlRequest.setValue(bearerToken, forHTTPHeaderField: HTTPHeaderField.authentication.rawValue)

    // Parameters
    if let parameters = parameters {
        do {
            urlRequest.httpBody = try JSONSerialization.data(withJSONObject: parameters, options: [])
        } catch {
            throw AFError.parameterEncodingFailed(reason: .jsonEncodingFailed(error: error))
        }
    }

    return urlRequest
}

以下是alamofire请求：

 import Foundation
import Alamofire

public class APIClient {
@discardableResult
private static func performRequest<T:Decodable>(route:APIRouter, decoder: JSONDecoder = JSONDecoder(), completion:@escaping (AFResult<T>)->Void) -> DataRequest {

    return AF.request(route)
                    .responseDecodable (decoder: decoder){ (response: AFDataResponse<T>) in
                        completion(response.result)
                        print("framework response::",response.result)
    }
}

public static func taskID(id: String, completion:@escaping (AFResult< [TaskID]>)->Void) {

    performRequest(route: APIRouter.TaskById(id: id), completion: completion)
}


}//APIClient

<代码>导入基础 进口阿拉莫菲尔 公共类客户端{ @可丢弃结果 私有静态func performRequest（路由：APIRouter，解码器：JSONDecoder=JSONDecoder（），完成：@escaping（AFResult）->Void）->DataRequest{ 返回AF.request（路由） .responseDecodable（解码器：解码器）{（响应：AFDataResponse）在 完成（响应、结果） 打印（“框架响应：：”，response.result） } } public static func taskID（id:String，completion:@escaping（AFResult<[taskID]>）->Void）{ performRequest（路由：APIRouter.TaskById（id:id），完成：完成） } }//APIClient 最初它显示的是字典，Swift.DecodingError.Context（codingPath:[]，debugDescription:“本应解码字典，但却找到了一个数组。但现在我在控制台日志中得到了nil。不知道为什么会得到nil值。根据我的json响应，struct是否正确？我正在努力获取嵌套数据

---

非常感谢您的任何帮助。

您的结构是正确的。请参阅下面的游乐场以获得证明；我没有得到错误。

nil

是非常常见的结果，当您没有完整的数据集，并且您假设响应中的某个可选字段是非可选的，因为您在示例数据中看到它（您的样品不一定具有代表性）。如果服务器没有实际的规范，您需要找出哪些字段无法解码，并且可能需要获取一组数据以确定哪些字段是真正可选的。您可以通过在上面的AF项目中输入错误处理代码或将响应粘贴到下面的“我的游乐场”中来完成此操作。无论哪种方式，解码ing错误应该告诉您哪个字段不存在

import PlaygroundSupport
import UIKit
import WebKit


public struct TaskID: Decodable {

let embedded: Embedded?
let count: Int?

enum CodingKeys: String, CodingKey {
    case count = "count"
    case embedded = "_embedded"
  }
}

 public struct Embedded: Decodable {


let task: [Task]?
enum CodingKeys: String, CodingKey {
       case task = "task"
   }

 }

public struct Task : Decodable {

let id : String?
let name: String?
let assignee: String?
let created: String?
let processDefinitionId: String?
enum CodingKeys: String, CodingKey {
    case id = "id"
    case name = "name"
    case assignee = "assignee"
    case created = "created"
    case processDefinitionId = "processDefinitionId"


 }

}


let data = """
{
"_links": {
    "self": {
        "href": "/task"
    }
},
"_embedded": {

    "task": [
        {
            "_links": {
                "assignee": {
                    "href": "/user/demo"
                },
                "execution": {
                    "href": "/execution/1b64cf75-0616-11ea-8860-120ef5ab2c25"
                },
                "identityLink": {
                    "href": "/task/1b64f688-0616-11ea-8860-120ef5ab2c25/identity-links"
                },
                "processDefinition": {
                    "href": "/process-definition/quickEvaluation:1:129ce2b1-0616-11ea-8860-120ef5ab2c25"
                },
                "processInstance": {
                    "href": "/process-instance/1b64cf75-0616-11ea-8860-120ef5ab2c25"
                },
                "self": {
                    "href": "/task/1b64f688-0616-11ea-8860-120ef5ab2c25"
                }
            },
            "_embedded": {
                "variable": []
            },
            "id": "1b64f688-0616-11ea-8860-120ef5ab2c25",
            "name": "Quick Evaluation",
            "assignee": "demo",
            "created": "2019-11-13T13:04:20.687+0000",
            "due": null,
            "followUp": null,
            "delegationState": null,
            "description": null,
            "executionId": "1b64cf75-0616-11ea-8860-120ef5ab2c25",
            "owner": null,
            "parentTaskId": null,
            "priority": 50,
            "processDefinitionId": "quickEvaluation:1:129ce2b1-0616-11ea-8860-120ef5ab2c25",
            "processInstanceId": "1b64cf75-0616-11ea-8860-120ef5ab2c25",
            "taskDefinitionKey": "QuickEvaluation",
            "caseExecutionId": null,
            "caseInstanceId": null,
            "caseDefinitionId": null,
            "suspended": false,
            "formKey": "a8apps:suryoday:gng:v0.1.0:kycUpload",
            "tenantId": null
        },
        {
            "_links": {
                "assignee": {
                    "href": "/user/demo"
                },
                "execution": {
                    "href": "/execution/412a03b7-06ae-11ea-8860-120ef5ab2c25"
                },
                "identityLink": {
                    "href": "/task/412a2aca-06ae-11ea-8860-120ef5ab2c25/identity-links"
                },
                "processDefinition": {
                    "href": "/process-definition/quickEvaluation:1:129ce2b1-0616-11ea-8860-120ef5ab2c25"
                },
                "processInstance": {
                    "href": "/process-instance/412a03b7-06ae-11ea-8860-120ef5ab2c25"
                },
                "self": {
                    "href": "/task/412a2aca-06ae-11ea-8860-120ef5ab2c25"
                }
            },
            "_embedded": {
                "variable": [
                    {
                        "_links": {
                            "self": {
                                "href": "/process-instance/412a03b7-06ae-11ea-8860-120ef5ab2c25/variables/loanAmount"
                            }
                        },
                        "_embedded": null,
                        "name": "loanAmount",
                        "value": "650000",
                        "type": "String",
                        "valueInfo": {}
                    },
                    {
                        "_links": {
                            "self": {
                                "href": "/process-instance/412a03b7-06ae-11ea-8860-120ef5ab2c25/variables/firstName"
                            }
                        },
                        "_embedded": null,
                        "name": "firstName",
                        "value": "Kamesh",
                        "type": "String",
                        "valueInfo": {}
                    }
                ]
            },
            "id": "412a2aca-06ae-11ea-8860-120ef5ab2c25",
            "name": "Quick Evaluation",
            "assignee": "demo",
            "created": "2019-11-14T07:13:27.558+0000",
            "due": null,
            "followUp": null,
            "delegationState": null,
            "description": null,
            "executionId": "412a03b7-06ae-11ea-8860-120ef5ab2c25",
            "owner": null,
            "parentTaskId": null,
            "priority": 50,
            "processDefinitionId": "quickEvaluation:1:129ce2b1-0616-11ea-8860-120ef5ab2c25",
            "processInstanceId": "412a03b7-06ae-11ea-8860-120ef5ab2c25",
            "taskDefinitionKey": "QuickEvaluation",
            "caseExecutionId": null,
            "caseInstanceId": null,
            "caseDefinitionId": null,
            "suspended": false,
            "formKey": "a8apps:suryoday:gng:v0.1.0:kycUpload",
            "tenantId": null
        }

    ]
},
"count": 13
}
""".data(using: .utf8)!

let decoder = JSONDecoder()
do {
  let decoded = try decoder.decode(TaskID.self, from: data)
  print(decoded)
} catch ( let error ) {
  print(error.localizedDescription)
}

此外，如果您感到懒惰，您可以使用，因为

nil

是来自decodable的一个非常常见的响应，您可以使用DataRequest的扩展来解析请求并从请求中获取值，就像使用

responseDecodable

，这里您可以使用类似的方法

 extension DataRequest {
    fileprivate func decodableResponseSerializer<T: Decodable>() -> DataResponseSerializer<T> {
        return DataResponseSerializer { _, response, data, error in
            guard error == nil else { return .failure(error!) }

            guard let data = data else {
                return .failure(AFError.responseSerializationFailed(reason: .inputDataNil))
            }

            return Result { try newJSONDecoder().decode(T.self, from: data) }
        }
    }

    @discardableResult
    fileprivate func responseDecodable<T: Decodable>(queue: DispatchQueue? = nil, completionHandler: @escaping (DataResponse<T>) -> Void) -> Self {
        return response(queue: queue, responseSerializer: decodableResponseSerializer(), completionHandler: completionHandler)
    }
}

扩展数据请求{
fileprivate func decodableResponseSerializer（）->DataResponseSerializer{
返回DataResponseSerializer{}，响应，数据，中的错误
guard error==nil else{return.failure（error！）}
guard let data=其他数据{
return.failure（AFError.responseSerialization失败（原因：.inputDataNil））
}
返回结果{try newJSONDecoder（）.decode（T.self，from:data）}
}
}
@可丢弃结果
fileprivate func responseDecodable（队列：DispatchQueue？=nil，completionHandler:@escaping（DataResponse）->Void）->Self{
返回响应（队列：队列，响应序列化程序：decodableResponseSerializer（），completionHandler:completionHandler）
}
}

然后你可以这样称呼它

Alamofire.request(url, method:.post, parameters: parameters, headers: headers)
        .responseDecodable { (response: DataResponse< Task >) in completion(response.result) }

Alamofire.request（url，方法：.post，参数：参数，标题：标题）
.responseDecodable{（响应：DataResponse）正在完成（response.result）}

---

当您得到类似的结果时，只有当您有不同类型的数据而不是您指定的数据时，才会出现此问题。

谢谢您的回答。.我怀疑我是否需要传入数组或类。func taskID（id:String，completion:@escaping（AFResult）->void仍然面临相同的问题我也有url请求代码。你能检查一下吗包装器是

TaskID

，就像我的例子一样。不用使用AF ResponsedCodeTable，只需要获取数据并自己解码，这样你就可以捕捉解码错误并找出哪个字段失败了。这和另外两个任务有什么区别你最近几天发布的离子？它们看起来非常相似。@JoakimDanielson最后两个问题我有编码键，希望解码字典，但找到了一个数组。但是现在我得到了零值。你能帮我解决这个问题吗this@JoakimDanielson现在我有了url请求代码，但我和其他人已经试过帮助你一次了对于你的json，你似乎仍然在为同样的事情而挣扎。我并不认为这有什么意义，因为没有什么真正的改变。你需要用你的代码来区分可能的问题，实际的json解码（这很好）以及您需要的AF和ApiClient类have@JoakimDanielson，好的，我有一个疑问，我是否需要在数组中传递结构名，还是只传递类名。公共静态func taskID（id:String，completion:@escaping（AFResult<[taskID]>）如果我传递taskID，它会显示错误，预期会解码字典，但找到数组。如果我改为数组[taskID]它打印零值。

Alamofire.request(url, method:.post, parameters: parameters, headers: headers)
        .responseDecodable { (response: DataResponse< Task >) in completion(response.result) }