如何从 JSON 响应中检索特定数据？

Question

目前，我正在使用 Google 地图距离矩阵 API，当我运行以下代码时得到以下结果：

func configureRoute(origin:String,destination:String){
    let jsonURL = "https://maps.googleapis.com/maps/api/distancematrix/json?units=imperial&origins=place_id:\(origin)&destinations=place_id:\(destination)&key=MYAPIKEY"
    guard let url = URL(string: jsonURL ) else {return}

    URLSession.shared.dataTask(with: url) { (data, response, err) in

        guard let data = data else {return}

        let dataAsString = String(data: data, encoding: .utf8)
        print(dataAsString)
        }.resume()
    }

这是结果：

Optional("{\n   \"destination_addresses\" : [ \"Pittsburgh, PA, USA\" ],\n   \"origin_addresses\" : [ \"Philadelphia, PA, USA\" ],\n   \"rows\" : [\n      {\n         \"elements\" : [\n            {\n               \"distance\" : {\n                  \"text\" : \"305 mi\",\n                  \"value\" : 490750\n               },\n               \"duration\" : {\n                  \"text\" : \"4 hours 48 mins\",\n                  \"value\" : 17257\n               },\n               \"status\" : \"OK\"\n            }\n         ]\n      }\n   ],\n   \"status\" : \"OK\"\n}\n")

但是根据这个结果，我只想得到距离的持续时间，在本例中是 4 小时 48 分钟。我怎么只得到持续时间？

在尝试了一些建议后，我放置了 JSON url 以获得格式化的结构并得到以下结果：

struct Welcome: Codable {
let destinationAddresses, originAddresses: [String]
let rows: [Row]
let status: String

enum CodingKeys: String, CodingKey {
    case destinationAddresses = "destination_addresses"
    case originAddresses = "origin_addresses"
    case rows, status
}
}

struct Row: Codable {
let elements: [Element]
 }

struct Element: Codable {
let distance, duration: Distance
let status: String
}

struct Distance: Codable {
let text: String
let value: Int
 }

使用它，我实现了以下代码：

func configureRoute(origin:String,destination:String){
    let jsonURL = "https://maps.googleapis.com/maps/api/distancematrix/json?units=imperial&origins=place_id:\(origin)&destinations=place_id:\(destination)&key=MYAPIKEY"
    guard let url = URL(string: jsonURL ) else {return}
    print(jsonURL)

    URLSession.shared.dataTask(with: url) { (data, response, err) in

        guard let data = data else {return}

        do{
            let route = try JSONDecoder().decode(Element.self, from: data)
            print (route.duration)
        }
        catch let jsonErr{

        }
        let dataAsString = String(data: data, encoding: .utf8)
//            print(dataAsString)
        }.resume()
}

但是我 route.duration 的结果仍然没有。

Answer 1

使用 SwiftyJSON：

进口SwiftyJSON

func configureRoute(origin:String,destination:String){
    let jsonURL = "https://maps.googleapis.com/maps/api/distancematrix/json?units=imperial&origins=place_id:\(origin)&destinations=place_id:\(destination)&key=MYAPIKEY"
    guard let url = URL(string: jsonURL ) else {return}

    URLSession.shared.dataTask(with: url) { (data, response, err) in

        guard let data = data else {return}

        let dataAsString = String(data: data, encoding: .utf8)
        if let json = JSON(data: data){
            if let durationValue = json["rows"][0]["elements"][0]["duration"]["value"].int32 {
            //This is duration seconds, 17257
        }

        if let durationText = json["rows"][0]["elements"][0]["duration"]["text"].stringValue {
           //this is duration text, 4 hours 48 mins
        }
        print(dataAsString)
        }.resume()
    }

Answer 2

将您的 JSON 回复粘贴到以下在线 json 到 swift 结构转换器中。 JSON String to Swift struct converter
```
{
"name": "John",
"age": 31,
"city": "New York"
}
```

现在复制生成的结构。

struct JSON: Codable {
 let name: String
 let age: Int
 let city: String
}

解码您的数据响应。不要忘记 try catch 和错误处理

let jsonRespone:JSON = try JSONDecoder().decode(JSON.self, data);

现在您可以使用您的结构访问数据。如果您的 JSON 响应包含一些并不总是存在的信息（例如错误消息），只需将您的 JSON 结构或该特定键设为可选即可。
```
let cityName:String = jsonResponse.city
let age:Int = jsonResponse.age
let name:String = jsonResponse.name
```

如何从 JSON 响应中检索特定数据？

How to retrieve specific data from JSON response?

ios

json

swift4

google-distancematrix-api