src\model\model.go

package model

import "strconv"

type User struct {
	username string
	password string
	age int32
}

func (this *User) String() string {
	return "username: " + this.username + " password: " + this.password + " age:" + strconv.Itoa(int(this.age))
}

注意,User的所有属性都是私有的

当我们创建 u := &User{}的时候,有没有办法将其属性赋值?

src\main\main.go

package main

import (
	"fmt"
	. "model"
	"unsafe"
	"reflect"
)

//type SliceHeader struct {
//	Data uintptr
//	Len  int
//	Cap  int
//}


func main() {
	var size int
	var str string
	size = int(unsafe.Sizeof(str))
	fmt.Println(size) 	// 16


	u := &User{} // User的所有成员变量都是private
	fmt.Println("u :",u)
	size= int(unsafe.Sizeof(*u))
	fmt.Println(size)

	// 可以将其理解为，指想固定地址，并有长度的[]byte
	header := &reflect.SliceHeader {
		Data : uintptr(unsafe.Pointer(u)),Len	 : size,Cap  : size,}

	b := *(*[]byte)(unsafe.Pointer(header))
	println(len(b))
	//12
	fmt.Println(b)
	//[0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0]
	age := 27
	size = int(unsafe.Sizeof(&age))
	header = &reflect.SliceHeader {
		Data : uintptr(unsafe.Pointer(&age)),}
	b2 := *(*[]byte)(unsafe.Pointer(header))
	fmt.Println(b2)

	b[16 + 16] = b2[0]
	b[16 + 16 + 1] = b2[1]
	b[16 + 16 + 2] = b2[2]
	b[16 + 16 + 3] = b2[3]
	b[16 + 16 + 4] = b2[4]
	b[16 + 16 + 5] = b2[5]
	b[16 + 16 + 5] = b2[6]
	b[16 + 16 + 7] = b2[7]
	fmt.Println(b)
	fmt.Println("u :",u)


}

进入src同级目录

export GOPATH=`pwd`

go install main

./bin/main

输出

16
u : username: password: age:0
40
40
[0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0]
[27 0 0 0 0 0 0 0]
[0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 27 0 0 0 0 0 0 0]
u : username: password: age:27

不建议,修改string属性,如果非要修改,建议将User中的username和password string类型,修改为 [32]byte.

理解思路同,C语言.尤其是C++中对共享内存数据的处理.