解码 JSON 时出错 - keyNotFound(CodingKeys

Posted 2023-03-15

【中文标题】解码 JSON 时出错 - keyNotFound(CodingKeys

【英文标题】：Error when decoding JSON - keyNotFound(CodingKeys

【发布时间】：2018-11-19 14:58:47

【问题描述】：

我正在尝试通过网络解析 JSON 数据。下面你可以看到魔法发生的地方。

func getBookingsForDate(date: String, completionHandler: @escaping ([String:String]) -> Void )

struct bookings: Codable 

    var bookieName : String
    var bookieNumber: String
    var booked: String
    var bookingTime: String

    private enum Codingkeys: String, CodingKey

        case bookieName
        case bookieNumber
        case booked
        case bookingTime
    


let params = ["date":date]

let urlString = "http://mscissorss.pythonanywhere.com/getBookings/"
Alamofire.request(urlString, method: .get, parameters: params).responseJSON 
    response in
    switch response.result 
    case .success(let JSON):

        let decoder = JSONDecoder()
        guard let _ = response.data else
            return
        
        do 
            let loginDetails = try decoder.decode(bookings.self, from: response.data!)
            print(loginDetails)
         catch let err
            print(err)
        

        //let bookings = JSON as! NSDictionary
        //completionHandler(JSON)
        /*
        do 
            let decoder = JSONDecoder()
            let gitData = try decoder.decode(bookings.self, from: JSON)
            print(gitData.bookieName)

         catch let err 
            print("Err", err)
        
        */
        break
    case .failure(let error):
        print(error)
    

鉴于代码我收到以下错误消息：

keyNotFound(CodingKeys(stringValue: "bookieName", intValue: nil), Swift.DecodingError.Context(codingPath: [], debugDescription: "No value associated with key CodingKeys(stringValue: \"bookieName\", intValue: nil) (\"bookieName\").", underlyingError: nil))

我得到的 JSON 响应如下所示：

    0 =     
        booked = false;
        bookieName = "";
        bookieNumber = "";
        bookingTime = "10:00";
    ;
    1 =     
        booked = false;
        bookieName = "";
        bookieNumber = "";
        bookingTime = "10:30";
    ;
    10 =     
        booked = false;
        bookieName = "";
        bookieNumber = "";
        bookingTime = "15:00";
    ;
    11 =     
        booked = false;
        bookieName = "";
        bookieNumber = "";
        bookingTime = "15:30";
    ;
    12 =     
        booked = false;
        bookieName = "";
        bookieNumber = "";
        bookingTime = "16:00";
    ;
    13 =     
        booked = false;
        bookieName = "";
        bookieNumber = "";
        bookingTime = "16:30";
    ;
    14 =     
        booked = false;
        bookieName = "";
        bookieNumber = "";
        bookingTime = "17:00";
    ;
    15 =     
        booked = false;
        bookieName = "";
        bookieNumber = "";
        bookingTime = "17:30";
    ;
    16 =     
        booked = false;
        bookieName = "";
        bookieNumber = "";
        bookingTime = "18:00";
    ;
    2 =     
        booked = false;
        bookieName = "";
        bookieNumber = "";
        bookingTime = "11:00";
    ;

这是我第一次解码，所以如果你有答案，请尝试解释一下为什么我需要做出我需要的改变。

更新

将代码更改为@sh_khan 和@vadian 建议的代码后，它可以解析它，但是我仍然在解析的对象中收到此错误：

["1": MagicS.(unknown context at 0x106932738).bookings(bookieName: "", bookieNumber: "", booked: "false", bookingTime: "10:30"), 
"0": MagicS.(unknown context at 0x106932738).bookings(bookieName: "", bookieNumber: "", booked: "false", bookingTime: "10:00"),

另外，如果我希望能够访问单个值，让我们说带有键 "0" -> bookieName 的第一项，我将如何使用 loginDetails 来做到这一点

【问题讨论】：

您不是用“11”键管理第一级（例如，实际上是所有其他键）。您可以使用当前代码解码的内容类似于："booked":false,"bookieName":"","bookieNumber":"","bookingTime":"10:00"。

【参考方案1】：

首先booked 是Bool，如果您不重命名密钥，则不需要private enum Codingkeys

struct Booking: Codable 

   let bookieName : String
   let bookieNumber: String
   let booked: Bool
   let bookingTime: String

第二次这样解码

let loginDetails = try decoder.decode([String:Booking].self, from: response.data!)

【讨论】：

解析成功上下文就是你写类的地方

我不明白你的意思。你能用另一种方式解释吗？ @sh_Khan

你的上下文是 projectName.className

【参考方案2】：

根对象是具有String 键和Bookings 值的字典 - 请以大写字母开头命名结构。

所以你必须解码

let loginDetails = try decoder.decode([String:Bookings].self, from: response.data!)

【讨论】：

unknown context 与 keyNotFound(CodingKeys 的问题无关。而 MagicS 是什么？获取特定的值关键就写loginDetails["0"]!.bookieName

MagicS 是我的 swift 项目的名称。感谢您回答其他问题 @vadian