package main

import (
	"encoding/json"
	"fmt"
)

type User struct {
	Name string `json:"name"`
}

func main() {
	var u User
	fmt.Printf("u=%+v, &u=%p\n", u, &u) //output: u={Name:}, &u=0xc00003e230
	json.Unmarshal([]byte(`{"name":"polaris"}`), &u)
	fmt.Printf("u.Name=%+v\n", u.Name) //output: u.Name=polaris

	//var u1 *User
	//fmt.Printf("u1=%+v, &u1=%p\n", u1, &u1) //output: u1=<nil>, &u1=0xc00007a028
	//json.Unmarshal([]byte(`{"name":"polaris"}`), u1)
	////以上会直接报错：panic: runtime error: invalid memory address or nil pointer dereference
	//fmt.Printf("u1.Name=%+v\n", u1.Name)

	var u2 *User
	fmt.Printf("u2=%+v, &u2=%p\n", u2, &u2) //output: u2=<nil>, &u2=0xc00007a028
	json.Unmarshal([]byte(`{"name":"polaris"}`), &u2)
	fmt.Printf("u2.Name=%+v\n", u2.Name) //正常打印出u2.Name=polaris

	/**
	总结：
		json.Unmarshal()第二个参数必须传入一个有内存地址的变量
	*/
}