Type problem in JSON conversion

[Andres_Latorre]

Hello,

I was wondering why when doing a Marshal and an Unmarshal the numbers are always taken as float64.

Here I put the replication of the error:

package main

import (
	"fmt"
	"encoding/json"
)

type abc struct {
	Name string
	Data interface{}
}
			

func main() {
	var idUser int64 = 1
	a := abc {
		"Abc",
		map[string]interface{}{
			"id_user": idUser, // string - int64
			"name": "a", // string - string
			"id_a": 1, // string - int
			"id_b": 1.2, // string - float
		},
	}
	b, _ := json.Marshal(a)
	
	// verify types
	var data abc
	_ = json.Unmarshal(b, &data)	
	values := data.Data.(map[string]interface{})	
	for k, v := range values{
		fmt.Printf("type key: %T, type value: %T\n", k, v)
	}
}

https://play.golang.org/p/Ax014b0JK3E

Would it be a bug in the functions of the json package from go?

Thanks to everyone beforehand

[NobbZ (Norbert Melzer)]

As JSON does only know floats, that’s correct. If though you use typed JSON decoders, you can also read them as int or json.Number.

[thenorthnate (Nathan North)]

This probably goes without saying, but if you know your fields ahead of time, you can always provide type in the struct itself rather than using “interface{}”.

Something like this:
https://play.golang.org/p/jlC2vsfX45V

[Andres_Latorre]

Hi @thenorthnate

It is with an external library. What I did was replicate the scenario.

Thanks for the reply.

[Andres_Latorre]

Hi @NobbZ

Thanks for the reply.