How to save a JSON file into csv - json

Question

I am trying to save this astros.json file into csv file.
Everything is working I don't have any error but my code is not going into my for loop.
So the astros.csv file is created successfully but there are no datas inside.
package main
import (
"encoding/json"
"encoding/csv"
"fmt"
"io/ioutil"
"os"
"net/http"
"strconv"
)
type People struct {
Name string
Craft string
}
type General struct {
//People []People
Number int
Message string
}
func main() {
// Reading data from JSON File
response, err := http.Get("http://api.open-notify.org/astros.json")
if err != nil {
fmt.Printf("The Http request failed with error %s\n", err)
}
data,_ := ioutil.ReadAll(response.Body)
//fmt.Println(string(data))
// Unmarshal JSON data
var general []General
json.Unmarshal([]byte(data), &general)
//fmt.Printf("First person: %s, Message: %s", general.People[0].Name, general.Message)
// Create a csv file
csvdatafile, err := os.Create("./astros.csv")
if err != nil {
fmt.Println(err)
}
defer csvdatafile.Close()
// Write Unmarshaled json data to CSV file
w := csv.NewWriter(csvdatafile)
for _, obj := range general {
fmt.Println("Are you going into the for ?")
var record []string
//record = append(record, obj.People)
record = append(record, strconv.Itoa(obj.Number), obj.Message)
record = append(record, obj.Message)
//record = append(record, []string{People})
w.Write(record)
fmt.Println("Are you coming here")
record = nil
}
w.Flush()
fmt.Println("Appending succed")
}

Answer 1

It is important to always check for errors; if you change your code to:
err = json.Unmarshal([]byte(data), &general)
if err != nil {
fmt.Printf("Error in unmarshall %s\n", err)
return
}
Then you would see the problem; json.Unmarshal is returning cannot unmarshal object into Go value of type []main.General. This means that general is nil so your loop is never entered.
The reason for this is apparent when you compare the JSON:
{
"people": [{
"name": "Christina Koch",
"craft": "ISS"
}, {
"name": "Alexander Skvortsov",
"craft": "ISS"
}, {
"name": "Luca Parmitano",
"craft": "ISS"
}, {
"name": "Andrew Morgan",
"craft": "ISS"
}, {
"name": "Oleg Skripochka",
"craft": "ISS"
}, {
"name": "Jessica Meir",
"craft": "ISS"
}
],
"number": 6,
"message": "success"
}
With the variable you are unmarshalling into; []General where General is:
type General struct {
//People []People
Number int
Message string
}
It looks like you had the right idea at some point with the []People but then commented it out.
If you uncomment []People, unmarshal into a General (rather than []General) then make your loop for _, obj := range general.People { it should work as expected. This assumes that you want to iterate through the people; general.Message and general.Number are also available (but you dont need a loop to access these).
See this example (have removed file operation as the playground does not support that).

Answer 2

you could try something like this:
package main
import (
"encoding/csv"
"encoding/json"
"fmt"
"net/http"
"os"
"strconv"
)
type People struct {
Name string
Craft string
}
type Response struct {
People []People
Number int
Message string
}
func main() {
// Reading data from JSON File
r, err := http.Get("http://api.open-notify.org/astros.json")
if err != nil {
fmt.Printf("The Http request failed with error %s\n", err)
}
var response Response
err = json.NewDecoder(r.Body).Decode(&response)
if err != nil {
fmt.Printf("decoding error%s\n", err)
return
}
// Create a csv file
csvdatafile, err := os.Create("./astros.csv")
if err != nil {
fmt.Println(err)
}
defer csvdatafile.Close()
// Write Unmarshaled json data to CSV file
w := csv.NewWriter(csvdatafile)
for _, obj := range response.People {
fmt.Println("Are you going into the for ?")
var record []string
//record = append(record, obj.People)
record = append(record, strconv.Itoa(response.Number), response.Message)
record = append(record, obj.Name)
// record = append(record, []string{obj})
w.Write(record)
fmt.Println("Are you coming here")
record = nil
}
w.Flush()
fmt.Println("Appending succed")
}