为什么去写000 / s而不是字符串？

Question

For some reasons go encodes the string like bytes and I'm wondering if it's a go bug. See the code below:

ip, _, err := net.ParseCIDR(cidr)
if err!=nil{
     log.Panicf("can't parse cidr %s, err was %v", cidr, err)
}

type Ip struct{
     Ip string
}

ips := string(ip)
j:= Ip{
     Ip: ips,
}
b, err := json.Marshal(j)
if err != nil {
     log.Printf("error:", err)
}

fmt.Fprintln(w, string(b))

It prints:

{"Ip":"\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\ufffd\ufffd\ufffd\ufffd\u0007+"}

I'm running Go from epel repository ( redhat ). I also made a snippet which returns similar results.

Play it for me!

Answer 1

This happens because you are treating a sequence of IP address bytes as a raw string.

The net.IP value returned by net.ParseCIDR has a .String() method you should call, instead of doing string(ip).

Try this instead:

package main

import (
    "encoding/json"
    "fmt"
    "log"
    "net"
)

func main() {
    cidr := "172.162.21.84/32"

    ip, _, err := net.ParseCIDR(cidr)
    if err != nil {
        log.Panicf("can't parse cidr %s, err was %v", cidr, err)
    }

    type Ip struct {
        Ip string
    }

    fmt.Printf("%T: %v
", ip, ip)

    j := Ip{
        Ip: ip.String(),
    }

    b, err := json.Marshal(j)
    if err != nil {
        log.Printf("error:", err)
    }

    fmt.Println(string(b))
}