转化为json格式
func Marshal(v interface{}) ([]byte, error) //将v（一般为结构体)转化为json格式
// json.go
package main
import (
"encoding/json"
"fmt"
"log"
"os"
)
type Address struct {
Type string
City string
Country string
}
type VCard struct {
FirstName string
LastName string
Addresses []*Address
Remark string
}
func main() {
pa := &Address{"private", "Aartselaar", "Belgium"}
wa := &Address{"work", "Boom", "Belgium"}
vc := VCard{"Jan", "Kersschot", []*Address{pa, wa}, "none"}
// fmt.Printf("%v: \n", vc) // {Jan Kersschot [0x126d2b80 0x126d2be0] none}:
// JSON format:
js, _ := json.Marshal(vc)
fmt.Printf("JSON format: %s", js)
}
结果：
{"FirstName":"Jan","LastName":"Kersschot","Addresses":[{"Type":"private","City":
"Aartselaar","Country":"Belgium"},{"Type":"work","City":"Boom","Country":"Belgiu
m"}],"Remark":"none"}
func MarshalIndent(v any, prefix string, indent string) ([]byte, error)
Code:
data := map[string]int{ "a": 1, "b": 2, } b, err := json.MarshalIndent(data, "<prefix>", "<indent>") if err != nil { log.Fatal(err) } fmt.Println(string(b))
Output:
{
<prefix><indent>"a": 1,
<prefix><indent>"b": 2
<prefix>}
func main() {
pa := &Address{"private", "Aartselaar", "Belgium"}
wa := &Address{"work", "Boom", "Belgium"}
vc := VCard{"Jan", "Kersschot", []*Address{pa, wa}, "none"}
// fmt.Printf("%v: \n", vc) // {Jan Kersschot [0x126d2b80 0x126d2be0] none}:
// JSON format:
js, _ := json.MarshalIndent(vc, " ", " ")
fmt.Printf("JSON format: %s", js)
}
结果：
{
"FirstName": "Jan",
"LastName": "Kersschot",
"Addresses": [
{
"Type": "private",
"City": "Aartselaar",
"Country": "Belgium"
},
{
"Type": "work",
"City": "Boom",
"Country": "Belgium"
}
],
"Remark": "none"
}
反序列化
func Unmarshal(data []byte, v interface{}) //error 把 JSON 解码为数据结构。
func main() {
pa := &Address{"private", "Aartselaar", "Belgium"}
wa := &Address{"work", "Boom", "Belgium"}
vc := VCard{"Jan", "Kersschot", []*Address{pa, wa}, "none"}
js, _ := json.MarshalIndent(vc, " ", " ")
fmt.Printf("%s\n", js)
var _vc VCard
json.Unmarshal(js, &_vc)
fmt.Println(_vc.FirstName, _vc.LastName, _vc.Addresses[0], _vc.Addresses[1], _vc.Remark)
}
结果：
{
"FirstName": "Jan",
"LastName": "Kersschot",
"Addresses": [
{
"Type": "private",
"City": "Aartselaar",
"Country": "Belgium"
},
{
"Type": "work",
"City": "Boom",
"Country": "Belgium"
}
],
"Remark": "none"
}
Jan Kersschot &{private Aartselaar Belgium} &{work Boom Belgium} none
解码任意的数据：
json 包使用 map[string]interface{} 和 []interface{} 储存任意的 JSON 对象和数组；其可以被反序列化为任何的 JSON blob 存储到接口值中。
例子：
b := []byte(`{"Name": "Wednesday", "Age": 6, "Parents": ["Gomez", "Morticia"]}`)
var f interface{}
err := json.Unmarshal(b, &f)
//f指向的是一个mpakey 是一个字符串，value 是自身存储作为空接口类型的值：
map[string]interface{} {
"Name": "Wednesday",
"Age": 6,
"Parents": []interface{} {
"Gomez",
"Morticia",
},
}
使用类型断言：
m := f.(map[string]interface{})
可以通过 for range 语法和 type switch 来访问其实际类型：
for k, v := range m {
switch vv := v.(type) {
case string:
fmt.Println(k, "is string", vv)
case int:
fmt.Println(k, "is int", vv)
case []interface{}:
fmt.Println(k, "is an array:")
for i, u := range vv {
fmt.Println(i, u)
}
default:
fmt.Println(k, "is of a type I don’t know how to handle")
}
}
解码数据到结构
如果我们事先知道 JSON 数据，我们可以定义一个适当的结构并对 JSON 数据反序列化:
type FamilyMember struct {
Name string
Age int
Parents []string
}
var m FamilyMember
err := json.Unmarshal(b, &m)
编码和解码流
json 包提供 Decoder 和 Encoder 类型来支持常用 JSON 数据流读写。NewDecoder() 和 NewEncoder() 函数分别封装了 io.Reader 和 io.Writer 接口。
func NewDecoder(r io.Reader) *Decoder func NewEncoder(w io.Writer) *Encoder
要想把 JSON 直接写入文件，可以使用 json.NewEncoder 初始化文件（或者任何实现 io.Writer 的类型），并调用 Encode()；反过来与其对应的是使用 json.NewDecoder 和 Decode() 函数：
func NewDecoder(r io.Reader) *Decoder
func (dec *Decoder) Decode(v interface{}) error
func main() {
pa := &Address{"private", "Aartselaar", "Belgium"}
wa := &Address{"work", "Boom", "Belgium"}
vc := VCard{"Jan", "Kersschot", []*Address{pa, wa}, "none"}
j, _ := os.OpenFile("json.txt", os.O_CREATE|os.O_RDWR|os.O_TRUNC, 0666)
j_encoder := json.NewEncoder(j)
j_encoder.Encode(vc)
defer j.Close()
}
func main() {
var vc VCard
j, _ := os.Open("./json.txt")
defer j.Close()
j_Decoder := json.NewDecoder(j)
j_Decoder.Decode(&vc)
fmt.Println(vc.FirstName, vc.LastName, vc.Addresses[0], vc.Addresses[1], vc.Remark)
}
标签：vc,string,fmt,Belgium,json,Address,go From： https://www.cnblogs.com/dadishi/p/17060851.html