如何用这个json来构造结构？

Question

如何用这个JSON建立一个结构模型？我在youtube上看过很多教程，但我仍然很困惑，在结构上使用enum有什么意义呢？

{
  "err_code": 0,
  "data": {
    "message": "Success",
    "result": {
      "check_in": [
        {
          "created_at": "2022-06-20 10:00:37",
          "late": "True",
          "location": "Jl. H. Asmawi No.63, Beji, Kecamatan Beji, Kota Depok, Jawa Barat 16421, Indonesia",
          "place": "GRIT OFFICE",
          "folder": "./pegawai/grit/2022/06/20/masuk/10/00/",
          "filename": "0000_rakha_fatih_athallah_picture.jpg",
          "tujuan": "",
          "link": "http://103.140.90.10:8081/face-recognition/client/python/pegawai/grit/2022/06/20/masuk/10/00/0000_rakha_fatih_athallah_picture.jpg"
        },
        {
          "created_at": "2022-06-16 11:23:12",
          "late": "True",
          "location": "Jl. H. Asmawi No.63, Beji, Kecamatan Beji, Kota Depok, Jawa Barat 16421, Indonesia",
          "place": "GRIT OFFICE",
          "folder": "./pegawai/grit/2022/06/16/masuk/11/23/",
          "filename": "0000_rakha_fatih_athallah_picture.jpg",
          "tujuan": "",
          "link": "http://103.140.90.10:8081/face-recognition/client/python/pegawai/grit/2022/06/16/masuk/11/23/0000_rakha_fatih_athallah_picture.jpg"
        }
      ],
      "check_out": []
    }
  }
}

这是我的结构模型。这一点很重要，因为我想在这个结构中使用This解码器。我想稍后再使用using解码器。

import Foundation

struct jsonData : Codable{
    var err_code : Int
    var data : Data
    
    enum CodingKeys: String, CodingKey {
            case err_code = "err_code"
            case data = "data"
        }
}

struct Data: Codable{
    var message : String
    var result  : Result
}

struct Result : Codable {
    var check_in  : [Checkin] = []
}

struct Checkin : Codable{
    var created_at : String
    var late : String
    var location : String
    var place : String
    var folder : String
    var tujuan : String
    var link : String
    
    enum CodingKeys: String, CodingKey {
            case created_at = "created_at"
            case late = "late"
            case location = "location"
            case place = "place"
            case folder = "folder"
            case tujuan = "tujuan"
            case link = "link"
        }
}

Answer 1

我认为您所拥有的结构非常接近所需的内容，只是一些小的调整，例如：

struct Response: Codable{
    var err_code: Int
    var data: DataObj
}

struct DataObj: Codable{
    var message: String
    var result: Result
}

struct Result: Codable {
    var check_in: [Checkin]
}

struct Checkin: Codable, Hashable {
    var created_at: String
    var late: String
    var location: String
    var place: String
    var folder: String
    var tujuan: String
    var link: String
}

像这样使用它：

struct ContentView: View {
    @State var apiResponse: Response?
    
    var body: some View {
        VStack {
            if let response = apiResponse {
                Text("message: \(response.data.message) ")
                Text("check_in.count: \(response.data.result.check_in.count) ")
            List {
                ForEach(response.data.result.check_in, id: \.self) { chk in
                    Text("created_at: \(chk.created_at) ")
                }
            }
            }
        }
        .onAppear {
            let jsonStr = """
                 {
                 "err_code": 0,
                 "data": {
                 "message": "Success",
                 "result": {
                 "check_in": [
                 {
                 "created_at": "2022-06-20 10:00:37",
                 "late": "True",
                 "location": "Jl. H. Asmawi No.63, Beji, Kecamatan Beji, Kota Depok, Jawa Barat 16421, Indonesia",
                 "place": "GRIT OFFICE",
                 "folder": "./pegawai/grit/2022/06/20/masuk/10/00/",
                 "filename": "0000_rakha_fatih_athallah_picture.jpg",
                 "tujuan": "",
                 "link": "http://103.140.90.10:8081/face-recognition/client/python/pegawai/grit/2022/06/20/masuk/10/00/0000_rakha_fatih_athallah_picture.jpg"
                 },
                 {
                 "created_at": "2022-06-16 11:23:12",
                 "late": "True",
                 "location": "Jl. H. Asmawi No.63, Beji, Kecamatan Beji, Kota Depok, Jawa Barat 16421, Indonesia",
                 "place": "GRIT OFFICE",
                 "folder": "./pegawai/grit/2022/06/16/masuk/11/23/",
                 "filename": "0000_rakha_fatih_athallah_picture.jpg",
                 "tujuan": "",
                 "link": "http://103.140.90.10:8081/face-recognition/client/python/pegawai/grit/2022/06/16/masuk/11/23/0000_rakha_fatih_athallah_picture.jpg"
                 }
                 ],
                 "check_out": []
                 }
                 }
                 }
                 """
            // simulated response data
            let data = jsonStr.data(using: .utf8)!
            do {
                self.apiResponse = try JSONDecoder().decode(Response.self, from: data)
                print("\n---> apiResponse \(apiResponse)")
            }
            catch {
                print(" error \(error)")
            }
        }
    }
}

Answer 2

我们使用CodingKeys，以便为JSON中的名称使用自定义名称。

例如，您有created_at，但不需要下划线，您要做的是将变量命名为createdAt，并在enum中添加case createdAt = "created_at"

至于解码部分，其实很简单：

do {
    //let data = the json data you got.
    let decoder = JSONDecoder()
    let model = try decoder.decode(jsonData.self, from: data)
}catch {
    print(String(describing: error))
}

请注意，我们在命名structs, classes, actors & enums时不使用小写字母。

编辑:感谢Marek R指出，有时JSON中的名称可以匹配特定于所用语言的关键字(即：Swift)，因此实现CodingKeys是必要的。