#GO学习笔记07
###一、map
1.定义
package main
import "fmt"
func main() {
//map只有len,没有cap
var m1 map[int]string
fmt.Println("m1 = ", m1)
fmt.Println("len = ", len(m1))
fmt.Println("-----------")
//make方式创建
m2 := make(map[int]string)
fmt.Println("m2 = ", m2)
fmt.Println("len = ", len(m2))
fmt.Println("-----------")
//指定长度2
m3 := make(map[int]string, 2)
m3[1] = "java"
m3[2] = "go"
m3[3] = "python"
fmt.Println("m3 = ", m3)
fmt.Println("len = ", len(m3))
}
m1 = map[]
len = 0
-----------
m2 = map[]
len = 0
-----------
m3 = map[1:java 2:go 3:python]
len = 3
2.迭代
package main
import "fmt"
func main() {
m := map[int]string{1: "java", 2: "go", 3: "python"}
for key, value := range m {
fmt.Printf("key = %d, value = %s\n", key, value)
}
value, ok := m[0]
if ok == true {
fmt.Println("m[0] = ", value)
} else {
fmt.Println("不存在")
}
value1, ok1 := m[1]
if ok1 == true {
fmt.Println("m[0] = ", value1)
} else {
fmt.Println("不存在")
}
}
key = 1, value = java
key = 2, value = go
key = 3, value = python
不存在
m[0] = java
3.删除
m := map[int]string{1: "java", 2: "go", 3: "python"}
for key, value := range m {
fmt.Printf("key = %d, value = %s\n", key, value)
}
delete(m, 1)
fmt.Println("m = ",m)
key = 1, value = java
key = 2, value = go
key = 3, value = python
m = map[2:go 3:python]
4.作为参数传递
import "fmt"
func main() {
m := map[int]string{1: "java", 2: "go", 3: "python"}
test(m) //引用传递
fmt.Println("m = ", m)
}
func test(m map[int]string) {
delete(m, 1)
}
m = map[2:go 3:python]
###二、结构体
1.定义
package main
import "fmt"
type Student struct {
id int
name string
age int
}
func main() {
//顺序初始化每个成员必须初始化
var s1 Student = Student{1,"tony",18}
fmt.Println("s1 = ",s1)
//指定初始化，未初始化的参数默认为类型的默认值
s2:=Student{name:"Tom",age:19}
fmt.Println("s2 = ",s2)
}
s1 = {1 tony 18}
s2 = {0 Tom 19}
2.指针类型的结构体
package main
import "fmt"
type Student struct {
id int
name string
age int
}
func main() {
//顺序初始化每个成员必须初始化
var p1 *Student = &Student{1,"tony",18}
fmt.Println("p1 = ",p1)
//指定初始化，未初始化的参数默认为类型的默认值
p2:=&Student{name:"Tom",age:19}
fmt.Println("p2 = ",p2)
}
p1 = &{1 tony 18}
p2 = &{0 Tom 19}
3.结构体普通成员操作
package main
import "fmt"
type Student struct {
id int
name string
age int
}
func main() {
var s Student
s.id = 1
s.name = "tony"
s.age = 19
fmt.Println("s = ", s)
}
s = {1 tony 19}
4.结构体指针成员的操作
package main
import "fmt"
type Student struct {
id int
name string
age int
}
func main() {
var s Student
var p1 *Student
p1 = &s
//第一种
p1.id = 1
p1.name = "tony"
p1.age = 19
fmt.Println("p1 = ", p1)
//第二种
p2 := new(Student)
p2.id = 2
p2.age = 18
p2.name = "tom"
fmt.Println("p2 = ", p2)
}
p1 = &{1 tony 19}
p2 = &{2 tom 18}
5.结构体的比较和赋值
结构体和数组一样可以赋值和比较
代码略
6.机构体作为函数参数01
package main
import "fmt"
type Student struct {
id int
name string
age int
}
func main() {
s := Student{1, "tony", 18}
test01(s)
fmt.Println("main: ", s)
}
func test01(student Student) {
student.id = 888
fmt.Println("test01 = ", student)
}
test01 = {888 tony 18}
main: {1 tony 18}
7.结构体作为函数参数02
package main
import "fmt"
type Student struct {
id int
name string
age int
}
func main() {
s := Student{1, "tony", 18}
test01(&s)
fmt.Println("main: ", s)
}
func test01(p *Student) {
p.id = 888
fmt.Println("test01 = ", p)
}
test01 = &{888 tony 18}
main: {888 tony 18}
8.可见性
如果想使用别的包里面的函数、结构体类型、结构体成员
函数名字、类型名、机构体成员变量名，首字母必须大写
