JSON 解组 Go 中的有符号整数数组

Question

I am trying to unmarshal JSON from an array of integers into a byte slice in Go.

The problem is we can do this only when the array in JSON contains positive integers as it will be recognized as uint8 in Go. It doesn't work when the array contains negative integers.

For example:

• this array will work: [1, 2, 3, 4, 5]
• this array will not work: [-14, 2, 3, 4, 5] (-14 is negative)

This is the error message that I received

Cannot unmarshal config file; err= json: cannot unmarshal number -14 int to Go struct field <struct_field> of type uint8

Is there any way I can do JSON unmarshal array with negative integers into a byte slice in Go?

Answer 1

Is there any way I can do JSON unmarshal array with negative integers into a byte slice in Go?

No, because negative numbers are outside of the valid range of byte values , just as any number greater than 255 is.

Answer 2

Thank you all for the answers.

I found the solution: Since I want a byte array and byte cannot hold signed int, what I can do is to convert the signed int to unsigned first in the JSON input offline, then I can do JSON unmarshal with the new unsigned array.

Link to playground: https://play.golang.org/p/Th2DC9AGeEs

Code for reference:

package main

import (
    "fmt"
)

func main() {
    arr := []int8{-14,1,2,3,4}
    var bytes []byte
    for _, val := range arr {
        bytes = append(bytes, convertToByte(val))
    }
    fmt.Println(bytes) // will print [242 1 2 3 4]
}

func convertToByte(value int8) byte {
    return byte(value)
}