从 API 响应的 json 检索数据

Question

I'm trying to get data from json response by storing it in some structs (Airport + coordinates) but I don't know how to deal with that since I'm not good enough with maps and interfaces. The code is showing no errors but MapofAirports is completely empty here is the code:

package main

import (
    //"api/client"
    //"api/client/clienterrors"
    //"api/client/openstreetmap"
    "encoding/json"
    "fmt"
    "io/ioutil"
    "log"
    "math"
    "net/http"
    "os"
    "strconv"
    "strings"
)

type Coordinates struct {
    Longitude string `json:"lon"`
    Latitude  string `json:"lat"`
}

type Airport struct {
    Co       Coordinates `json:"location"`
    IATACode string      `json:"id"`
    Distance float64     `json:"distance"` // distance to coordinates in kilometer
}

func GetCoordinatesFromURL(url string) (float64, float64) {

    parts := strings.Split(url, "=")

    lat0 := strings.Split(parts[2], "&")
    lon0 := strings.Split(parts[3], "&")

    lat1, _ := strconv.ParseFloat(lat0[0], 64)
    lon1, _ := strconv.ParseFloat(lon0[0], 64)

    return lat1, lon1
}

func CalcDistance(lat1 float64, long1 float64, lat2 float64, long2 float64) float64 {

    var latitude1 = lat1 * math.Pi / 180
    var latitude2 = lat2 * math.Pi / 180
    var longitude1 = long1 * math.Pi / 180
    var longitude2 = long2 * math.Pi / 180

    var R = 6371.0
    var d = R * math.Acos(math.Cos(latitude1)*math.Cos(latitude2)*math.Cos(longitude2-longitude1)+math.Sin(latitude1)*math.Sin(latitude2))

    return d
}

func main() {
    var Locations []Airport
    Locations = make([]Airport, 0)

    var url = fmt.Sprintf("https://api.skypicker.com/locations?type=radius&lat=40.730610&lon=-73.935242&radius=250&location_types=airport&limit=3&sort=id&active_only=true")

    UrlLat, UrlLon := GetCoordinatesFromURL(url)

    resp, err := http.Get(url)
    if err != nil {
        panic(err.Error())
    }
    defer resp.Body.Close()
    body, err := ioutil.ReadAll(resp.Body)

    var airportsJsonResponse interface{}

    err = json.Unmarshal(body, &airportsJsonResponse)

    MapofAirports, ok := airportsJsonResponse.([]interface{})

    if ok {
        lenAiroMap := len(MapofAirports)

        locationsMaps := make(map[int]map[string]interface{})

        for i := 0; i < lenAiroMap; i++ {
            locationsMaps[i] = MapofAirports[i].(map[string]interface{})
        }
        var coords Coordinates
        for i := 0; i < lenAiroMap; i++ {
            if longitude, ok0 := locationsMaps[i]["lon"].(string); ok0 {
                if latitude, ok1 := locationsMaps[i]["lat"].(string); ok1 {
                    coords = Coordinates{longitude, latitude}
                }
            }
            code := locationsMaps[i]["id"].(string)

            latFromCoordinates, _ := strconv.ParseFloat(Locations[i].Co.Latitude, 64)
            lonFromCoordinates, _ := strconv.ParseFloat(Locations[i].Co.Longitude, 64)

            dist := CalcDistance(latFromCoordinates, lonFromCoordinates, UrlLat, UrlLon)
            Locations = append(Locations, Airport{
                Co:       coords,
                IATACode: code,
                Distance: dist,
            })
        }
    }
    LocationsJson, err := json.Marshal(Locations)
    if err != nil {
        log.Fatal("Cannot encode to JSON ", err)
    }
    fmt.Fprintf(os.Stdout, "%s", LocationsJson)
}

screenshot of json response

in the screenshot this is the json response we have, and I'm processing like this:

{ locations[],meta,last_refresh,results_retrieved } ==> location : { id , location + distance(calculated with a function) }

Answer 1

Change this line MapofAirports, ok:= airportsJsonResponse.([]interface{}) to this

MapofAirports, ok := airportsJsonResponse.(map[string]interface{})

If you place a break point at this line you will see type of airportsJsonResponse is map[string]interface{} . And you will have to change this lines into key value iteration

for i := 0; i < lenAiroMap; i++ {
            locationsMaps[i] = MapofAirports[i].(map[string]interface{})
        }

in to sth like below:

        lenAiroMap := len(MapofAirports)
        locationsMaps := make([]map[string]interface{},lenAiroMap)
        for i, value := range MapofAirports["locations"].([]interface{}) {
            converted := value.(map[string]interface{})
            locationsMaps[i] = converted
        }

Answer 2

this is my last update and while running the program it panics at unmarshaling step

package main

import (
    "encoding/json"
    "fmt"
    "io/ioutil"
    "math"
    "net/http"
    "strconv"
    "strings"
)

type Coordinates struct {
    Longitude string `json:"lon"`
    Latitude  string `json:"lat"`
}

type Airport struct {
    Co       Coordinates `json:"location"`
    IATACode string      `json:"id"`
    Distance float64     `json:"distance"` // distance to coordinates in kilometer
}

type Response struct {
    Locations []Airport `json:"locations"`
    // add all the other fields you care about
}

func GetCoordinatesFromURL(url string) (float64, float64) {

    parts := strings.Split(url, "=")

    lat0 := strings.Split(parts[2], "&")
    lon0 := strings.Split(parts[3], "&")

    lat1, _ := strconv.ParseFloat(lat0[0], 64)
    lon1, _ := strconv.ParseFloat(lon0[0], 64)

    return lat1, lon1
}

func CalcDistance(lat1 float64, long1 float64, lat2 float64, long2 float64) float64 {

    var latitude1 = lat1 * math.Pi / 180
    var latitude2 = lat2 * math.Pi / 180
    var longitude1 = long1 * math.Pi / 180
    var longitude2 = long2 * math.Pi / 180

    var R = 6371.0
    var d = R * math.Acos(math.Cos(latitude1)*math.Cos(latitude2)*math.Cos(longitude2-longitude1)+math.Sin(latitude1)*math.Sin(latitude2))

    return d
}

func main() {


    var url = fmt.Sprintf("https://api.skypicker.com/locations?type=radius&lat=40.730610&lon=-73.935242&radius=250&location_types=airport&limit=3&sort=id&active_only=true")

    UrlLat, UrlLon := GetCoordinatesFromURL(url)

    resp, err := http.Get(url)
    if err != nil {
        panic(err.Error())
    }
    defer resp.Body.Close()

     data, err := ioutil.ReadAll(resp.Body)
    res := &Response{}
    if err := json.Unmarshal(data, res); err != nil {
        panic(err)
    }
    fmt.Println(res.Locations)

    for i, item := range res.Locations {
        latt,_ := strconv.ParseFloat(item.Co.Latitude, 64)
        lonn,_ :=strconv.ParseFloat(item.Co.Longitude, 64)
        res.Locations[i].Distance = CalcDistance(latt,lonn , UrlLat, UrlLon)
    }
    fmt.Println("after calculate distance")
    fmt.Println(res.Locations)
}

what's wrong with that?