如何在同一个容器中解码 DynamicKeys 和 CodingKeys？

问题描述

考虑以下 JSON：我正在尝试解码“团队”对象。

let jsonString = """

{
   "Superheroes":{
   "Marvel":"107","DC":"106"
},"teams":{
  "106":{
     "name":"Marvel","Superheroes":{
        "890":{
           "name":"Batman"
        }
     }
  },"107":{
     "name":"DC","Superheroes":{
        "891":{
           "name":"Wonder Woman"
        }
     }
   }
  }
}

"""

我尝试过这样的事情：

struct SuperheroResponse: Decodable {

    let teams: [Team]

    private enum CodingKeys: String,CodingKey {

        case teams = "teams"
    }

    private struct DynamicCodingKeys: CodingKey {
        var stringValue: String
        init?(stringValue: String) {
            self.stringValue = stringValue
        }

        var intValue: Int?
        init?(intValue: Int) {
            return nil
        }
    }

    init(from decoder: Decoder) throws {

        let container = try decoder.container(keyedBy: CodingKeys.self)
        let teamContainer = try container.nestedContainer(keyedBy: CodingKeys.self,forKey: CodingKeys.teams)
        print(teamContainer.allKeys.count)
    
        let tempArray: [Team] = []

        for key in teamContainer.allKeys {

            let decodedobject = try teamContainer.decode(Team.self,forKey: DynamicCodingKeys(stringValue: key.stringValue)!)
            tempArray.append(decodedobject)
        }

        teams = tempArray
   }
}

struct Team: Decodable {

    let name: String
}

我想首先我会得到团队容器，映射键并从那里继续。问题是 teamContainer.allKeys.count 始终为零。

还有以下行，导致以下错误：无法将类型“SuperheroResponse.DynamicCodingKeys”的值转换为预期的参数类型“SuperheroResponse.CodingKeys”

let decodedobject = try teamContainer.decode(Team.self,forKey: DynamicCodingKeys(stringValue: key.stringValue)!)

最后我解码如下：

let jsonData = Data(jsonString.utf8)
let decodedResult = try! JSONDecoder().decode(SuperheroResponse.self,from: jsonData)

dump(decodedResult)

任何帮助将不胜感激。理想情况下，我想要像 SuperheroResponse -> [Team] 这样的东西， Team -> name,[Superhero],Superhero -> name

解决方法

您只是犯了几个小错误。你快到了。

团队容器由 DynamicCodingKeys 键控：

let teamContainer = try container.nestedContainer(keyedBy: DynamicCodingKeys.self,// <=
                                                  forKey: .teams)

并且可以使用您提供的密钥对团队进行解码：

let decodedObject = try teamContainer.decode(Team.self,forKey: key)

另外，tempArray 必须是 var:

var tempArray: [Team] = []

或者用 map 替换该循环：

    teams = try teamContainer.allKeys.map {
        try teamContainer.decode(Team.self,forKey: $0)
    }

一起：

init(from decoder: Decoder) throws {
    let container = try decoder.container(keyedBy: CodingKeys.self)
    let teamContainer = try container.nestedContainer(keyedBy: DynamicCodingKeys.self,forKey: .teams)
    teams = try teamContainer.allKeys.map {
        try teamContainer.decode(Team.self,forKey: $0)
    }
}