使用 Swift Decodable 解析 JSON 时出现类型不匹配错误

Question

当我尝试解码JSON时，出现错误：

(错误：typeMismatch(Swift.String， Swift.DecodingError.Context(codingPath： [sweetyanime.视频。(_D1045E05CDE474AEBA8BDCAF57455DC3中的编码键(.video，sweetyanime.iD。(CodingKeys in _D1045E05CDE474AEBA8BDCAF57455DC3(.ID， sweetyanime.other.(_D1045E05CDE474AEBA8BDCAF57455DC3中的编码键(。CountOfVideos]，debugDescription："预期解码字符串，但找到了一个字典。

1( JSON：

{ "video":{  
  "ID":{ 
     "Name":"NameOfAnime",
     "Describe":"SomeDescribe",
     "Image":"https://firebasestorage.googleapis.com/v0/b/sweety-anime-e6bb4.appspot.com/o/main.png?alt=media&token=042a2dad-8519-4904-9ba3-262c2c962434",
     "CountOfVideos":{  
        "1Series":"https://firebasestorage.googleapis.com/v0/b/sweety-anime-e6bb4.appspot.com/o/message_movies%252F12323439-9729-4941-BA07-2BAE970967C7.movalt=media&token=978d8b3a-7aad-468f-87d4-2b587d616720"
     }
  } } }

2(快速代码：

let jsonUrl = "file:///Users/tima/WebstormProjects/untitled/db.json"
guard let url = URL(string: jsonUrl) else { return }
URLSession.shared.dataTask(with: url) { (data, reponse, error) in
    guard let data = data else {return}
    do {
        let video = try
            JSONDecoder().decode(Video.self, from: data)
        print(video.video.ID.Name)
    } catch let jsonErr {
        print("Error: ", jsonErr)
    }
}.resume()

3(视频.swift

struct Video: Decodable {
   private enum CodingKeys : String, CodingKey { case video = "video" 
   }
   let video: iD
}
struct iD: Decodable {
   private enum CodingKeys : String, CodingKey { case ID = "ID" }
   let ID: other
}
struct other: Decodable {
   private enum CodingKeys : String, CodingKey {
      case Name = "Name"
      case Describe = "Describe"
      case Image = "Image"
      case CountOfVideos = "CountOfVideos"
   }
   let Name: String
   let Describe: String
   let Image: String
   let CountOfVideos: String
}

Answer 1

让我们在错误消息中放置一些换行符以使其易于理解：

(Error: typeMismatch(Swift.String,
    Swift.DecodingError.Context(codingPath: [
        sweetyanime.Video.(CodingKeys in _D1045E05CDE474AEBA8BDCAF57455DC3).video,
        sweetyanime.iD.(CodingKeys in _D1045E05CDE474AEBA8BDCAF57455DC3).ID,
        sweetyanime.other.(CodingKeys in _D1045E05CDE474AEBA8BDCAF57455DC3).CountOfVideos],
    debugDescription: "Expected to decode String but found a dictionary instead.",
    underlyingError: nil)

所以它试图解码"CountOfVideos"的值。它需要一个字符串，但它找到了一个字典。

您需要定义一个与"CountOfVideos"字典对应的struct(它似乎包含一个键"1Series"，带有字符串值(，或者您需要从other结构中删除 CountOfVideos 属性，以便根本不尝试对其进行解码。

Answer 2

我的我认为你应该实现作为解码的一部分的 init(来自解码器(初始值设定项。与自动实现相比，它在如何处理嵌套 JSON 方面提供了更大的灵活性。一种可能的实现方式如下：

struct Video: Decodable {
let name: String
let describe: String
let image: String
let countOfVideos: String
private enum VideoKey: String, CodingKey {
    case video = "video"
}
private enum IDKey: String, CodingKey {
    case id = "ID"
}
private enum CodingKeys: String, CodingKey {
    case name = "Name"
    case describe = "Describe"
    case image = "Image"
    case countOfVideos = "CountOfVideos"
}
private enum VideoCountKey: String, CodingKey {
    case videoCount = "1Series"
}
init(from decoder: Decoder) throws {
    let videoContainer = try decoder.container(keyedBy: VideoKey.self)
    let idContainer = try videoContainer.nestedContainer(keyedBy: IDKey.self, forKey: .video)
    let valuesContainer = try idContainer.nestedContainer(keyedBy: CodingKeys.self, forKey: .id)
    self.name = try valuesContainer.decode(String.self, forKey: .name)
    self.describe = try valuesContainer.decode(String.self, forKey: .describe)
    self.image = try valuesContainer.decode(String.self, forKey: .image)
    let videoCountContainer = try valuesContainer.nestedContainer(keyedBy: VideoCountKey.self, forKey: .countOfVideos)
    self.countOfVideos = try videoCountContainer.decode(String.self, forKey: .videoCount)
}

这适用于操场中的示例数据。我真的不知道你是否想要视频计数的键或值。(对我来说，两者都不像是视频的数量。 通常，您只需要为嵌套 JSON 的每个级别定义一个 CodingKey 枚举，您就可以根据需要解码单个值。(注意，由于我只看到了您的数据的一个示例，因此这可能会在您正在使用的任何 API 中的某些内容上中断，因此请根据需要修改/采纳这些想法并重写它(