package main
import "fmt" 
    type Student struct {
        id   int
        name string
        sex  byte
        age  int
        addr string
    }
    
    func main() {
        //1、顺序初始化，必须每个成员都初始化
        var s1 Student = Student{1, "mike", 'm', 18, "sz"}
        s2 := Student{2, "yoyo", 'f', 20, "sz"}
        //s3 := Student{2, "tom", 'm', 20} //err, too few values in struct initializer
    
        //2、指定初始化某个成员，没有初始化的成员为零值
        s4 := Student{id: 2, name: "lily"}
        fmt.Println(s1,s2,s4)
        // {1 mike 109 18 sz} {2 yoyo 102 20 sz} {2 lily 0 0 }
    }
 

2.2 指针变量

package main
import "fmt" 
type Student struct {
    id   int
    name string
    sex  byte
    age  int
    addr string
}

func main() {
    var s5 *Student = &Student{3, "xiaoming", 'm', 16, "bj"}
    s6 := &Student{4, "rocco", 'm', 3, "sh"}
    fmt.Println(s5,s6)//&{3 xiaoming 109 16 bj} &{4 rocco 109 3 sh}
}
 

3 .结构体成员的使用

package main
import "fmt" 
type Student struct {
    id   int
    name string
    sex  byte
    age  int
    addr string
}
func main() {
   //===============结构体变量为普通变量
    //1、打印成员
    var s1  = Student{1, "mike", 'm', 18, "sz"}
    //结果：id = 1, name = mike, sex = m, age = 18, addr = sz
    fmt.Printf("id = %d, name = %s, sex = %c, age = %d, addr = %sn", s1.id, s1.name, s1.sex, s1.age, s1.addr)

    //2、成员变量赋值
    var s2 Student
    s2.id = 2
    s2.name = "yoyo"
    s2.sex = 'f'
    s2.age = 16
    s2.addr = "guangzhou"
    fmt.Println(s2) //{2 yoyo 102 16 guangzhou}
}
 

3.2 指针变量

package main
import "fmt" 
type Student struct {
    id   int
    name string
    sex  byte
    age  int
    addr string
}
func main() {
  //===============结构体变量为指针变量
    //3、先分配空间，再赋值
    s3 := new(Student)
    s3.id = 3
    s3.name = "xxx"
    fmt.Println(s3) //&{3 xxx 0 0 }

    //4、普通变量和指针变量类型打印
    var s4 Student = Student{4, "yyy", 'm', 18, "sz"}
    fmt.Printf("s4 = %v, &s4 = %vn", s4, &s4) //s4 = {4 yyy 109 18 sz}, &s4 = &{4 yyy 109 18 sz}

    var p *Student = &s4
    //p.成员 和(*p).成员 操作是等价的
    p.id = 5
    (*p).name = "zzz"
    fmt.Println(p, *p, s4) //&{5 zzz 109 18 sz} {5 zzz 109 18 sz} {5 zzz 109 18 sz}
}
 

4 .结构体比较

如果结构体的全部成员都是可以比较的，那么结构体也是可以比较的，那样的话两个结构体将可以使用 == 或 != 运算符进行比较，但不支持 > 或 < 。

package main
import "fmt" 
type Student struct {
    id   int
    name string
    sex  byte
    age  int
    addr string
}
func main() {
    s1 := Student{1, "mike", 'm', 18, "sz"}
    s2 := Student{1, "mike", 'm', 18, "sz"}

    fmt.Println("s1 == s2", s1 == s2) //s1 == s2 true
    fmt.Println("s1 != s2", s1 != s2) //s1 != s2 false
}

5 结构体作为函数参数

package main
import "fmt" 
type Student struct {
    id   int
    name string
    sex  byte
    age  int
    addr string
}
    func printStudentValue(tmp Student) {
        tmp.id = 250
        //printStudentValue tmp =  {250 mike 109 18 sz}
        fmt.Println("printStudentValue tmp = ", tmp)
    }
    func main() {
        var s Student = Student{1, "mike", 'm', 18, "sz"}
        printStudentValue(s)//值传递，形参的修改不会影响到实参
        fmt.Println("main s = ", s) //main s =  {1 mike 109 18 sz}
    }

5.2 引用传递

package main
import "fmt" 
type Student struct {
    id   int
    name string
    sex  byte
    age  int
    addr string
}
    func printStudentPointer(p *Student) {
        p.id = 250
        //printStudentPointer p =  &{250 mike 109 18 sz}
        fmt.Println("printStudentPointer p = ", p)
    }
    func main() {
        var s Student = Student{1, "mike", 'm', 18, "sz"}
        printStudentPointer(&s)//引用(地址)传递，形参的修改会影响到实参
        fmt.Println("main s = ", s)//main s =  {250 mike 109 18 sz}
    }

6. 可见性

Go语言对关键字的增加非常吝啬，其中没有private、 protected、 public这样的关键字。

要使某个符号对其他包（package）可见（即可以访问），需要将该符号定义为以大写字母 开头。

目录结构： 

test.go示例代码如下：

//test.go
package test

//student01只能在本文件件引用，因为首字母小写
type student01 struct {
    Id   int
    Name string
}

//Student02可以在任意文件引用，因为首字母大写
type Student02 struct {
    Id   int
    name string
}

main.go示例代码如下：

// main.go
package main

import (
    "fmt"
    "test" //导入test包
)

func main() {
    //s1 := test.student01{1, "mike"} //err, cannot refer to unexported name test.student01

    //err, implicit assignment of unexported field 'name' in test.Student02 literal
    //s2 := test.Student02{2, "yoyo"}
    //fmt.Println(s2)

    var s3 test.Student02 //声明变量
    s3.Id = 1             //ok
    //s3.name = "mike"  //err, s3.name undefined (cannot refer to unexported field or method name)
    fmt.Println(s3)
}