Golang Json Unmarshal数值与指数

Question

I have problem when Unmarshal json string into struct that is the numeric value with exponent will alway be 0. Please check code below :

package main

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

type Person struct {
    Id   uint64  `json:"id"`
    Name string `json:"name"`
}

func main() {

    //Create the Json string
    var b = []byte(`{"id": 1.2E+8, "Name": "Fernando"}`)

    //Marshal the json to a proper struct
    var f Person
    json.Unmarshal(b, &f)

    //print the person
    fmt.Println(f)

    //unmarshal the struct to json
    result, _ := json.Marshal(f)

    //print the json
    os.Stdout.Write(result)
}

And the run is :

{0 Fernando}

Is there any way to make it work? Since the exponent thing is standart JSON. It seems the golang wrong interpret it.

Here the playground : http://play.golang.org/p/8owgjX9y0m

Answer 1

Change the Id type from int64 to float32 or float64.

http://play.golang.org/p/-zidTD_q8y

EDIT: This may be a bit of a hack, but you can add a "dummy" Id field of type float64 and write a hook to cast the value to the actual Id type int64.

type Person struct {
    Id    float64          `json:"id"`
    _Id   int64             
    Name  string           `json:"name"`
}

var f Person
var b = []byte(`{"id": 1.2e+8, "Name": "Fernando"}`)
_ = json.Unmarshal(b, &f)

if reflect.TypeOf(f._Id) == reflect.TypeOf((int64)(0)) {
    fmt.Println(f.Id)
    f._Id = int64(f.Id)
}

http://play.golang.org/p/32HHLxnFlX