How to create a struct with different structs of one members of struct in go?

Question

I am getting a json response from a server with three fix json object field and one field with different json objects.

Example - Response 1

{
   status : "success",
   error-code : "",
   message : "login successful",
   data : {
           token : "token value",
           refresh-token : "refresh token value"
          }
}

Example - Response 2

{
   status : "success",
   error-code : "",
   message : "user data fetched",
   data : {
           first-name: "josh",
           last-name : "walter",
           age : "30",
           phone: 1234567890,
           address : "x street, dc"
          }
}

for above json response created struct as follows

type loginData struct {
    Token string `json:"token"`
    RefreshToken string `json:"refresh-token"`

}

type userdata {
    FirstName string    `json:"first-name"`
    LastName string     `json:"refresh-token"`
    Age string          `json:"age"`
    Phone string        `json:"phone"`
    Address string      `json:"address"`

}


type response struct {
    Status string       `json:"status"`
    ErrorCode string    `json:"error-code"`
    RespMessage string  `json:"message"`
    RespData string     `json:"data"`
}

How to add logindata struct while unmarshaling during login response and userdata struct while unmarshaling userdata response in "RespData" field in response struct

mkopriva · Accepted Answer · 2022-02-21 17:04:14Z

2

First change the RespData field's type:

type response struct {
    Status      string      `json:"status"`
    ErrorCode   string      `json:"error-code"`
    RespMessage string      `json:"message"`
    RespData    interface{} `json:"data"`
}

Then, depending on what request you are making, set the RespData field to a pre-allocated instance of a pointer to the expected type:

r, err := http.Get("https://some_api.com/loginData")
if err != nil {
    return err
}
defer r.Body.Close()

// check r.StatusCode and make sure it's correct

data := loginData{}
resp := response{RespData: &data}
if err := json.NewDecoder(r.Body).Decode(&resp); err != nil {
    return err
}

fmt.Println(data)

answered Feb 21, 2022 at 17:04

mkopriva

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4 Comments

Suyog Patil Over a year ago

please check code below added answer

mkopriva Over a year ago

@supapati what for should I check the code in "below added answer"?

Suyog Patil Over a year ago

whether it is correct as you said to do..

mkopriva Over a year ago

@supapati if it works then it's correct, wouldn't you say so?

Aswin Thiyagarajan · Accepted Answer · 2022-02-21 17:08:03Z

0

According to me, you should have two different structs to do this. One reason is separation of concern, as the structure of these responses may change in the future and these are responses from two different apis so its better to maintain different response objects.

type loginData struct {
    Token        string `json:"token"`
    RefreshToken string `json:"refresh-token"`
}

type userdata struct {
    FirstName string `json:"first-name"`
    LastName  string `json:"refresh-token"`
    Age       string `json:"age"`
    Phone     string `json:"phone"`
    Address   string `json:"address"`
}

type response struct {
    Status      string `json:"status"`
    ErrorCode   string `json:"error-code"`
    RespMessage string `json:"message"`
}

type userResponse struct {
    response
    RespData userdata `json:"data"`
}

type loginResponse struct {
    response
    RespData loginData `json:"data"`
}

answered Feb 21, 2022 at 17:08

Aswin Thiyagarajan

3652 silver badges8 bronze badges

3 Comments

Suyog Patil Over a year ago

I think this will workout will check n revert ..

Suyog Patil Over a year ago

I tried your suggestion but we get 27 different API responses in data field for each response, so have to create two struct each one child one parent. so there will be reusable code.

Aswin Thiyagarajan Over a year ago

This will tedious if you have too many apis, I guess @mkopriva is an easier approach.

Aswin Thiyagarajan · Accepted Answer · 2022-02-23 04:17:14Z

@mkopriva as you said tried this suggestion it worked.

package main

import (
    "encoding/json"
    "fmt"
    "strings"
)

type loginData struct {
    Token        string `json:"token"`
    RefreshToken string `json:"refresh-token"`
}

type userdata struct {
    FirstName string `json:"first-name"`
    LastName  string `json:"last-name"`
    Age       string `json:"age"`
    Phone     string `json:"phone"`
    Address   string `json:"address"`
}

type response struct {
    Status      string      `json:"status"`
    ErrorCode   string      `json:"error-code"`
    RespMessage string      `json:"message"`
    RespData    interface{} `json:"data"`
}

func main() {
    jsonresp_1 := `{
        "status" : "success",
        "error-code" : "",
        "message" : "login successful",
        "data" : {
                "token" : "token value",
                "refresh-token" : "refresh token value"
               }
     }`

    jsonresp_2 := `{
        "status" : "success",
        "error-code" : "",
        "message" : "user data fetched",
        "data" : {
                "first-name": "josh",
                "last-name" : "walter",
                "age" : "30",
                "phone": "1234567890",
                "address" : "x street, dc"
               }
     }`
    resp1 := strings.NewReader(jsonresp_1)
    data1 := loginData{}
    respdata1 := response{RespData: &data1}

    if err := json.NewDecoder(resp1).Decode(&respdata1); err != nil {
        fmt.Println(err)
    }
    fmt.Printf("token : %s \nrefreshtoken : %s \n", data1.Token, data1.RefreshToken)

    fmt.Println("-------------------")

    resp2 := strings.NewReader(jsonresp_2)
    data2 := userdata{}
    respdata2 := response{RespData: &data2}

    if err := json.NewDecoder(resp2).Decode(&respdata2); err != nil {
        fmt.Println(err)
    }
    fmt.Printf("firstname : %s \nlastname : %s ", data2.FirstName, data2.LastName)
}

Output

⚡ ⇒  go run main.go 
token : token value 
refreshtoken : refresh token value 
-------------------
firstname : josh 
lastname : walter

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