How to unmarshal struct into map in golang

Question

I have a Json:

{
  "id": "me",
  "name": "myname",
  "planets": {
      "EARTH": 3,
      "MARS": 4
  }
}

I don't know how to unmarshal planets field into map[string]int, so I'll get access to the elements without unmarshaling them too like in this example: json to map Golang

Here is the code:

package main

import (
   "encoding/json"
   "fmt"
  )

type User struct {
   ID      string `json:"id"`
   Name    string `json:"name"`
   Planets struct {
       Planet map[string]*json.RawMessage
    } `json:"planets"`
}

 func main() {
    data := `{
      "id": "me",
      "name": "myname",
      "planets": {
      "EARTH": 3,
       "MARS": 4
      }
    }`

   user := &User{}
   err := json.Unmarshal([]byte(data), user)
   if err != nil {
       fmt.Println("ERROR " + err.Error())
   }
    fmt.Println(user.ID)
    fmt.Println(user.Planets.Planet["EARTH"])
  }

fmt.Println(user.Planets.Planet["EARTH"]) - returns

fmt.Println(user.Planets["EARTH"]) - does not support indexing

Thank you for including the code. So what is the question? Your description seems to describe the expected behavior. — Jonathan Hall, Jan 23 '18 at 13:28
Please Write Problem Statement Correctly. There is not understanding with this. — nitin jain, Apr 09 '20 at 12:44

Eddy Hernandez · Accepted Answer · 2018-01-23T14:27:27.937

Here is an example with marshal and unmarshal using your object definition

package main

import (
    "encoding/json"
    "fmt"
)

type MyObject struct {
    ID      string         `json:"id"`
    Name    string         `json:"name"`
    Planets map[string]int `json:"planets"`
}

func main() {
    aa := &MyObject{
        ID:   "123",
        Name: "pepe",
        Planets: map[string]int{
            "EARTH": 3,
            "MARS":  4,
        },
    }
    // Marshal
    out, err := json.Marshal(aa)
    if err != nil {
        fmt.Println(err)
        return
    }
    fmt.Println(string(out))

    // Unmarshal
    bb := &MyObject{}
    err = json.Unmarshal(out, bb)
    fmt.Println(bb.ID, bb.Name, bb.Planets)

}

and you can get an element of the map with bb.Planets["EARTH"]

I hope you can find this useful.

How to unmarshal struct into map in golang

1 Answers1