Swift-解码深度嵌套词典

Question

我已经很接近了，但我很难找到一个非常简单的函数来访问JSON中嵌套的数据点。我使用的例子是在谷歌方向API。

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 u003cbu003enorthu003c/bu003e on u003cbu003eSalem Stu003c/bu003e toward u003cbu003eJerusalem Plu003c/bu003e",
"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"
}

可解码结构：为了处理此问题，我使用可解码。我已经能够访问一级嵌套数据(routes.summary(，但我很难再往下看(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设置后的实施：

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          
}

在所有这些之后，我所想做的就是能够访问JSON中的"文本"并返回该值。代码中的最后一行能够在JSON中成功返回"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=方向.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的结构键和循环中的以下内容：

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密钥，但它是一个起点。

如果键和结构成员具有相同的名称，则不需要指定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密钥，您必须添加适当的密钥解码策略

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

要访问数组([](，您必须通过索引获取项目

step[0]

或者使用循环迭代数组

for step in steps {}