使用Swift中的可解码代码解析嵌套JSON

我正在尝试解析这个JSON响应

    {
    "payload": {
        "bgl_category": [{
            "number": "X",
            "name": "",
            "parent_number": null,
            "id": 48488,
            "description": "Baustellenunterk\u00fcnfte, Container",
            "children_count": 6
        }, {
            "number": "Y",
            "name": "",
            "parent_number": null,
            "id": 49586,
            "description": "Ger\u00e4te f\u00fcr Vermessung, Labor, B\u00fcro, Kommunikation, \u00dcberwachung, K\u00fcche",
            "children_count": 7
        }]
    },
    "meta": {
        "total": 21
    }
}

我感兴趣的是在TableViewCell中查看

编号

和

说明

以下是我试图做的：

    //MARK: - BGLCats
struct BGLCats: Decodable {

        let meta : Meta!
        let payload : Payload!
        
}

//MARK: - Payload
struct Payload: Decodable {

        let bglCategory : [BglCategory]!
        
}

//MARK: - BglCategory
struct BglCategory: Decodable {

        let descriptionField : String
        let id : Int
        let name : String
        let number : String
        let parentNumber : Int
        
}

//MARK: - Meta
struct Meta: Decodable {

        let total : Int
        
}

API请求：

    fileprivate func getBgls() {
        
        guard let authToken = getAuthToken() else {
            return
        }
        
        let headers  = [
            "content-type" : "application/json",
            "cache-control": "no-cache",
            "Accept"       : "application/json",
            "Authorization": "\(authToken)"
        ]
        
        let request = NSMutableURLRequest(url: NSURL(string: "https://api-dev.com")! as URL, cachePolicy: .useProtocolCachePolicy, timeoutInterval: 10.0)
        
        request.allHTTPHeaderFields = headers
        
        let endpoint  = "https://api-dev.com"
        guard let url = URL(string: endpoint) else { return }
        
        URLSession.shared.dataTask(with: request as URLRequest) {(data, response, error) in
            guard let data = data else { return }
            
            do {
                let BGLList = try JSONDecoder().decode(BglCategory.self, from: data)
                print(BGLList)
                
                DispatchQueue.main.sync { [ weak self] in
                    self?.number = BGLList.number
                    self?.desc   = BGLList.descriptionField
//                    self?.id  = BGLList.id

                    print("Number: \(self?.number ?? "Unknown" )")
                    print("desc: \(self?.desc ?? "Unknown" )")
//                    print("id: \(self?.id ?? 0 )")
                }
            } catch let jsonError {
                print("Error Serializing JSON:", jsonError)
            }
            
       }.resume()
    }

但我得到了一个错误：

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

---

问题是JSONDecoder不知道例如

bglCategory

在JSON负载中表示为

bgl\u category

。如果JSON名称与变量名称不同，则需要将

CodingKeys

实现到

Decodable

就你而言：

struct BglCategory:可解码{
let descriptionField:字符串
让id:Int
let name:String
编号：String
让家长编号：Int？
枚举编码键：字符串，编码键{
案例id、名称、编号
案例描述字段=“描述”
case parentNumber=“parent\u number”
}
}
结构有效载荷：可解码{
让bglCategory:[bglCategory]！
枚举编码键：字符串，编码键{
案例bglCategory=“bgl\u类别”
}
}

这里有几个问题

您（基本上）正确地创建了模型，但只有两个不匹配：

struct BglCategory: Decodable {

   let description : String // renamed, to match "description" in JSON
   let parentNum: Int?      // optional, because some values are null
   // ...
}

第二个问题是，您的模型属性是camelCased，而JSON是snake\u cased。JSONDecoder有一个

.convertFromSnakeCase

开始功能来自动处理这个问题。在解码之前，您需要在解码器上设置它

第三个问题是您需要解码根对象

BGLCats

，而不是

BglCategory

let decoder = JSONDecoder()
decoder.keyDecodingStrategy = .convertFromSnakeCase // set the decoding strategy

let bglCats = try decoder.decode(BGLCats.self, from: data) // decode BGLCats

let blgCategories = bglCats.payload.bglCategory

---

错误消息与JSON和代码不匹配。您应该会遇到其他错误。在使用camelCased名称时，必须至少指定

convertFromSnakeCase

策略，根对象是

BGLCats

。请注意：如果有本机对应的类，请不要使用

NS…

类。