[golang] 使用Golang 抓取LASS JSON API的資訊

LASS的json api有2層的json結構，網路搜尋到的json範例，多是只能抓取一層，能抓取第2層的例子，卻只能在第2層放內建的int與float之類的資料型態，因LASS第2層資料用golang的json讀取後會形成一個map的資料結構，所以須使用interface陣列才能進去讀取第2層。

num_of_records這個欄位，轉換後的資料型態是float64，可以直接印出來，但如果要用於迴圈變數，須轉成整數n=int(m["num_of_records"].(float64))。

以下是程式碼。（保留網路上找來的parseArray()與parseMap()，以後可能會用到）

package main import (         "encoding/json"         "fmt"         "io/ioutil"         "net/http" ) func main() {         resp, err := http.Get("https://data.lass-net.org/data/last-all-lass.json")         jsonResponse, _ := ioutil.ReadAll(resp.Body)         var m map[string]interface{}         if err := json.Unmarshal(jsonResponse, &m); err != nil {                 fmt.Println("Fatal")                 panic(err)         }         if err != nil {                 fmt.Println("error: ", err)         } else {                 //fmt.Println(m)                 fmt.Println("ver=", m["version"])                 fmt.Println("src=", m["source"])                 fmt.Println("num=", m["num_of_records"])                 //fmt.Println("feeds=", m["feeds"].(map)) //how to extract records??         }         //parseMap(m)         //parseArray(m["feeds"].([]interface{}))         //fmt.Println("feeds[0]=", m["feeds"].([]interface{})[0].(map[string]interface{})["gps_num"])         //for lassData := range m["feeds"].([]interface{}) {         //n := m["num_of_records"].(type)         switch m["num_of_records"].(type) {         case string:                 fmt.Println("type is string")         case int:                 fmt.Println("type is int")         case float32:                 fmt.Println("type is float32")         case float64:                 fmt.Println("type is float64") //===> this is the answer         default:                 fmt.Println("type is unknown")         }         n := int(m["num_of_records"].(float64)) //n, ok := m["num_of_records"].(int) //bad ?         fmt.Println("n=", n)         for i, lassData := range m["feeds"].([]interface{}) {                 fmt.Println("------------ record # ", i, "------------")                 fmt.Print("device_id=", lassData.(map[string]interface{})["device_id"])                 fmt.Print(", SiteName=", lassData.(map[string]interface{})["SiteName"])                 fmt.Print(", gpsLat=", lassData.(map[string]interface{})["gpsLat"])                 fmt.Print(", gpsLon=", lassData.(map[string]interface{})["gpsLon"])                 fmt.Print(", timestamp=", lassData.(map[string]interface{})["timestamp"])                 fmt.Print(", s_d0=", lassData.(map[string]interface{})["s_d0"])                 fmt.Print(", s_d1=", lassData.(map[string]interface{})["s_d1"])                 fmt.Print(", s_d2=", lassData.(map[string]interface{})["s_d2"])                 fmt.Print(", s_h0", lassData.(map[string]interface{})["s_h0"])                 fmt.Println(", s_h1=", lassData.(map[string]interface{})["s_h1"])                 //fmt.Println("gps_num=", lassData.(map[string]interface{})["gps_num"])         } } func parseMap(aMap map[string]interface{}) {         for key, val := range aMap {                 switch concreteVal := val.(type) {                 case map[string]interface{}:                         fmt.Println("--- parseMap():map[string]interface{} --------")                         fmt.Println(key)                         parseMap(val.(map[string]interface{}))                 case []interface{}:                         fmt.Println("--- parseMap():[]interface{} --------")                         fmt.Println(key)                         parseArray(val.([]interface{}))                 default:                         fmt.Println("--- parseMap():default --------")                         fmt.Println(key, ":", concreteVal)                 }         } } func parseArray(anArray []interface{}) {         for i, val := range anArray {                 switch concreteVal := val.(type) {                 case map[string]interface{}:                         fmt.Println("--- parseArray():map[string]interface{} --------")                         fmt.Println("Index:", i)                         parseMap(val.(map[string]interface{}))                 case []interface{}:                         fmt.Println("--- parseArray():[]interface{} --------")                         fmt.Println("Index:", i)                         parseArray(val.([]interface{}))                 default:                         fmt.Println("--- parseArray():default --------")                         fmt.Println("Index", i, ":", concreteVal)                 }         } }