Json Api调用返回错误**keyNotFound**

我正在尝试进行api调用，我正在查询中构建api并像往常一样对其进行解析，但我遇到了错误：

keyNotFound（编码键（stringValue:“locationType”，intValue:nil），Swift.DecodingError.Context（编码路径：[[u JSONKey（stringValue:“索引0”，intValue:0）]，调试说明：“没有与键编码键相关联的值（stringValue:“locationType”，intValue:nil）（“locationType”）”，底层错误：nil**）

获取数据：

func fetchData(completionHandler: @escaping ([Root]) -> Void) {
    
    let queryItems = [URLQueryItem(name: "lat", value: "51.176519"),URLQueryItem(name: "lng", value: "-0.622557"),URLQueryItem(name: "date", value: "2020-11")]
    var urlComponents = URLComponents(string: "https://data.police.uk/api/crimes-street/all-crime")
    urlComponents?.queryItems = queryItems
    guard let combinedUrl = urlComponents?.url else {return}
    print(combinedUrl)
    let task = URLSession.shared.dataTask(with: combinedUrl,completionHandler : { (data, response, error) in
        if let error = error {
            print("Error with fetching accounts: \(error)")
            return
        }
        guard let httpResponse = response as? HTTPURLResponse,
              (200...400).contains(httpResponse.statusCode) else {
            print("Error with the response , unexpected status code:\(response)")
            return
        }
        guard let data = data else {return}
        do {
            let decoder = JSONDecoder()
            let dataSummary = try decoder.decode([Root].self, from: data)
            completionHandler(dataSummary.self ?? [])
        } catch {
            print(error)
        }
    })
    task.resume()
}

视图控制器：

    override func viewDidLoad() {
    super.viewDidLoad()
    networking.fetchData{[weak self] (jsonValues) in
        self?.jsonValues = jsonValues ;print("JSON values Inside closure : \(jsonValues)")
    }
    print("JSON values outside closure: \(jsonValues)")
}

根结构：

public struct Root: Codable {
public let category, location_Type: String
public let location: Location
public let context: String
public let outcomeStatus: OutcomeStatus
public let persistentId: String
public let id: Int
public let locationSubtype, month: String
public init(category: String, locationType: String, location: Location, context: String, outcomeStatus: OutcomeStatus, persistentId: String, id: Int, locationSubtype: String, month: String) {
    self.category = category
    self.locationType = locationType
    self.location = location
    self.context = context
    self.outcomeStatus = outcomeStatus
    self.persistentId = persistentId
    self.id = id
    self.locationSubtype = locationSubtype
    self.month = month
}

}

---

任何帮助都将是惊人的

错误表明它在API响应中发现了nil，因为我没有考虑到响应可以是nil，我在根结构中设置了可选值，然后它成功解析

public let category, location_Type: String?
public let location: Location
public let context: String
public let outcomeStatus: OutcomeStatus?
public let persistentId: String?
public let id: Int
public let locationSubtype, month: String?

---

将

print（jsonValues）

替换为

print（“闭包外的JSON值：\（jsonValues）”）

，并将

self？.jsonValues=jsonValues

替换为

self？.jsonValues=jsonValues；打印（“闭包内的JSON值：：\（self？.jsonValues）”）

，请先查看打印的内容？嘿，感谢您的评论，我已经替换了您推荐的内容。“”重写func viewdiload（）{super.viewdiload（）networking.fetchData{[weak self]（jsonValues）in self？.jsonValues=jsonValues；print（“闭包内的JSON值：（jsonValues）”）}''print（“闭包外的JSON值：（jsonValues）”）}它唯一要打印的是闭包外的JSON，闭包是空的[]现在，执行适当的

do{try}catch{}

而不是

try？

并打印错误。您当前只是忽略了错误。因此我添加了do catch block

do{let decoder=JSONDecoder（）let dataSummary=try decoder.decode（[Root].self，from:data）completionHandler（dataSummary.self？？？[]）catch{print（error.localizedDescription）}

错误是数据丢失，无法读取。不确定出了什么问题。不要打印本地化描述，只打印错误。