一、变量、常量
1.注意事项
导包必须使用、声明的变量必须使用、变量可以不赋值，默认值是系统默认值。
2.变量的声明和赋值
package main
import "fmt"
func main() {
var a int
a = 20
fmt.Println("a 的值是", a)
c := 30 //自动推导类型
fmt.Printf("c type is %T\n", c)
}
a 的值是 20
c type is int
//Println是换行输出 Printf是格式化输出
3.多重赋值
i, j := 10, 20
i, j = j, i
fmt.Printf("i = %d , j = %d \n", i, j)
//实现快速交换两个变量的值
4.匿名变量
package main
import "fmt"
func main() {
var o, p, q int
o, p, q = test()
fmt.Printf("o = %d, p = %d,q = %d\n", o, p, q)
//_代表匿名变量，可以忽略一个返回值
o, _, q = test()
fmt.Printf("o = %d,q = %d\n", o, q)
}
func test() (a, b, c int) {
return 1, 2, 3
}
5.常量
package main
import "fmt"
func main() {
const a = 10
fmt.Println("a的值是", a) //常量不允许再次赋值
const b = 11.2 //常量不用加冒号 const b: = 11.2
fmt.Printf("b type is %T\n", b)
fmt.Println("b =", b)
}
6.声明的时候简单写法
package main
import "fmt"
func main() {
//var a int
//var b float64
//也可以这样写 ,常量也一样
var (
a int
b float64
)
a, b = 10, 3.14
fmt.Println("a = ", a)
fmt.Println("b = ", b)
}
二、枚举
package main
import "fmt"
func main() {
//1.iota常量自动生成器，每隔一行自动累加1
//2.iota给常量赋值使用
const (
a = iota //0
b = iota //1
c = iota //2
d = iota //3
)
fmt.Printf("a = %d , b = %d , c = %d，d = %d\n", a, b, c, d)
//3.iota遇到const重置为0
const e = iota
fmt.Printf("e = %d\n", e)
//4.可以只写一个iota
const (
a1 = iota //0
b1
c1
)
fmt.Printf("a1 = %d , b1 = %d , c1 = %d\n", a1, b1, c1)
//5.在同一行的iota值一样
const (
o = iota
p1, p2, p3 = iota, iota, iota
q = iota
)
fmt.Printf("o = %d ,p1 = %d,p2= %d,p3 = %d,q = %d", o, p1, p2, p3, q)
}