Swift - 解码一个深度嵌套的字典

Question

我是如此接近 - 但我正在努力使用一个非常简单的函数来允许我访问深深嵌套在我的 JSON 中的数据点。我使用的示例是在 Google 方向 API 上。

示例 JSON(来自 GMapsAPI):

{
  "geocoded_waypoints" : [
  {
     "geocoder_status" : "OK",
     "partial_match" : true,
     "place_id" : "ChIJ960bMolw44kRQcGOlOZQ-r8",
     "types" : [ "premise" ]
  },
  {
     "geocoder_status" : "OK",
     "partial_match" : true,
     "place_id" : "EiMxMTggU2FsZW0gU3QsIEJvc3RvbiwgTUEgMDIxMTMsIFVTQSIaEhgKFAoSCSvDfDSJcOOJEbQanF0WxROfEHY",
     "types" : [ "street_address" ]
  }
],
"routes" : [
  {
     "bounds" : {
        "northeast" : {
           "lat" : 42.3647252,
           "lng" : -71.0555085
        },
        "southwest" : {
           "lat" : 42.3644965,
           "lng" : -71.05552419999999
        }
     },
     "copyrights" : "Map data ©2018 Google",
     "legs" : [
        {
           "distance" : {
              "text" : "82 ft",
              "value" : 25
           },
           "duration" : {
              "text" : "1 min",
              "value" : 11
           },
           "end_address" : "118 Salem St, Boston, MA 02113, USA",
           "end_location" : {
              "lat" : 42.3647252,
              "lng" : -71.0555085
           },
           "start_address" : "115 Salem St, Boston, MA 02113, USA",
           "start_location" : {
              "lat" : 42.3644965,
              "lng" : -71.05552419999999
           },
           "steps" : [
              {
                 "distance" : {
                    "text" : "82 ft",
                    "value" : 25
                 },
                 "duration" : {
                    "text" : "1 min",
                    "value" : 11
                 },
                 "end_location" : {
                    "lat" : 42.3647252,
                    "lng" : -71.0555085
                 },
                 "html_instructions" : "Head \u003cb\u003enorth\u003c/b\u003e on \u003cb\u003eSalem St\u003c/b\u003e toward \u003cb\u003eJerusalem Pl\u003c/b\u003e",
                 "polyline" : {
                    "points" : "ciqaG~_upLO?]A"
                 },
                 "start_location" : {
                    "lat" : 42.3644965,
                    "lng" : -71.05552419999999
                 },
                 "travel_mode" : "DRIVING"
              }
           ],
           "traffic_speed_entry" : [],
           "via_waypoint" : []
        }
     ],
     "overview_polyline" : {
        "points" : "ciqaG~_upLm@A"
     },
     "summary" : "Salem St",
     "warnings" : [],
     "waypoint_order" : []
  }
  ],
"status" : "OK"
}

Decodable Structure:为此，我使用了 Decodable。我已经能够访问第一级嵌套数据(routes.summary)，但我正在努力进一步深入(例如:routes.legs.duration)。我的代码结构如下:

struct Directions: Decodable {
    let status: String
    let routes: [Routes]

         enum CodingKeys :String, CodingKey {
              case status, routes
    }

struct Routes: Decodable {
    let summary: String
    let legs: [Legs]

         enum CodingKeys : String, CodingKey {
              case summary, legs
          }
}

struct Legs: Decodable {
    let duration: Duration

          enum CodingKeys : String, CodingKey {
          case duration
          }
    }

struct Duration: Decodable {
        let text: String    

            enum CodingKeys : String, CodingKey {
               case text
            }
        }

URL设置后的实现:

      URLSession.shared.dataTask(with: url) { (data, response, err) in
          guard let data = data else { return }
          do {   
             let directions = try
             JSONDecoder().decode(Directions.self, from: data)

        for item in directions.routes {
            self.stringoutput = item.summary          
       }

完成这一切后，我只想访问 JSON 中的“文本”并返回该值。代码最后一行能够成功返回JSON中的“summary”；我可以打印(方向)，整个数组/字典将在调试区域返回，包括“文本”。但我仍然不知道该怎么做:

x = directions.routes.legs.duration.text

使x等于“1分钟”

感谢任何人的帮助。

编辑:最终起作用的是下面 Vadian 的结构键和下面的 for in 循环:

                for item in directions.routes {
                    print(item.summary)
                    self.direct = item.summary
                    for items in item.legs {
                        self.stringoutput = items.duration.text
                        print(items.duration.text)
                        }

干杯!

Answer 1

这些结构不会解码所有键，但这是一个起点。

如果键和结构成员具有相同的名称，则无需指定 CodingKeys

struct Directions: Decodable {
    let status: String
    let routes: [Route]
}

struct Route: Decodable {
    let summary: String
    let legs: [Leg]
}

struct Leg: Decodable {
    let duration : TextValue
    let distance : TextValue
    let endAddress : String
    let endLocation : Location
    let startAddress : String
    let startLocation : Location
    let steps : [Step]
}

struct TextValue: Decodable {
    let text: String
    let value : Int
}

struct Location: Decodable {
    let lat, lng : Double
}

struct Step: Decodable {
    let duration : TextValue
    let distance : TextValue
    let endLocation : Location
    let startLocation : Location
    let htmlInstructions : String
    let travelMode : String
}

要正确解码 snake_cased key ，您必须添加适当的 key 解码策略

let decoder = JSONDecoder()
decoder.keyDecodingStrategy = .convertFromSnakeCase

要访问数组 ([])，您必须按索引获取项目

step[0]

或者循环遍历数组

for step in steps {}