Learn go language 0x07: stringer exercise code in go language journey

* subject

https://tour.go-zh.org/methods/18

practice ：Stringer
By making IPAddr Type implementation fmt.Stringer To print dot separated addresses .
for example ,IPAddr{1, 2, 3, 4} Should be printed as “1.2.3.4”.

* Implementation mode I ： Use strconv

strconv Use , Reference resources ：https://golang.google.cn/pkg/strconv/
strconv.Itoa(int(val)) Yes, it will int Integer to string .
because IPAddr yes 4 individual byte, So we need to use int(val) convert to int type .

package main

import "fmt"
import "strconv"

type IPAddr [4]byte

// TODO:  to  IPAddr  Add one  "String() string"  Method 
func (v IPAddr) String() string {
    
    var s string
    for idx, val := range v {
    
        if idx != 3 {
    
            s += strconv.Itoa(int(val)) + "."
        } else {
    
            s += strconv.Itoa(int(val))
        }
    }
    return s
}

func main() {
    
    hosts := map[string]IPAddr{
    
        "loopback":  {
    127, 0, 0, 1},
        "googleDNS": {
    8, 8, 8, 8},
    }
    for name, ip := range hosts {
    
        fmt.Printf("%v: %v\n", name, ip)
    }
}

Output ：

loopback: 127.0.0.1
googleDNS: 8.8.8.8

* Implementation mode II ： Use fmt.Sprintf

package main

import "fmt"

type IPAddr [4]byte

// TODO:  to  IPAddr  Add one  "String() string"  Method 
func (v IPAddr) String() string {
    
    return fmt.Sprintf("%v.%v.%v.%v", v[0], v[1], v[2], v[3])
}

func main() {
    
    hosts := map[string]IPAddr{
    
        "loopback":  {
    127, 0, 0, 1},
        "googleDNS": {
    8, 8, 8, 8},
    }
    for name, ip := range hosts {
    
        fmt.Printf("%v: %v\n", name, ip)
    }
}