[go-nuts] json unmarshal automatic type conversion issue

[arunkumar]

Hi gophers,

How to prevent json unmarshal from type conversion. From the below sample 
code i got the input string converted to float64


package main

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

func main() {
var output interface{}
var input = "1"
fmt.Println(reflect.TypeOf(input))
json.Unmarshal([]byte(input), &output)
fmt.Println(reflect.TypeOf(output)) 
}


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Re: [go-nuts] About the confusion caused by type conversion in golang

[Arunkumar Gudelli]

256 considered as `constant`. (untyped)
So when we try to convert to byte (which has a range from 0 to 255), it
will throw the overflow error.

Where `x := uint64(256)` we are giving a type to constant uint64.

y := byte(256) // Same error

so byte(uint64) will be zero without any errors.

regards,
Arun Gudelli
https://golangtutorial.dev/

On Thu, Jan 28, 2021 at 6:43 AM Barry Li  wrote:

> Some doubts about type conversion in go.
> In the following code, why can it be executed normally after passing the
> variable?
> The code is an error during the compilation phase.
>
> // The following two lines of code can be executed normally
> x := uint64(256)
> fmt.Println(byte(uint64(x))) // normal execution
>
> // The following code cannot be executed normally
> fmt.Println(byte(uint64(256))) // constant 256 overflows byte
>
> Can anyone help me answer it?
>
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> 
> .
>

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