golang-101-hacks(19)——switch

注:本文是对golang-101-hacks中文翻译。
和其他编程语言(例如C)相比,Go语音的switch-case语句不需要显式的添加"break",也没有fall-though。如下面代码所示:
Compared to other programming languages (such as C), Go's switch-case statement doesn't need explicit "break", and not have fall-though characteristic. Take the following code as an example:

package main
import (
 "fmt"
)
func checkSwitch(val int) {
 switch val {
 case 0:
 case 1:
 fmt.Println("The value is: ", val)
 }
}
func main() {
 checkSwitch(0)
 checkSwitch(1)
}

输出结果是

The value is: 1

期望当val为0或1时,执行fmt.Println("The value is: ", val),但实际上,该语句只在val为1时生效。为了得到期望结果,有两种方法:
使用fallthrough:

func checkSwitch(val int) {
 switch val {
 case 0:
 fallthrough
 case 1:
 fmt.Println("The value is: ", val)
 }
}

(2)将0和1放在同一个的case语句下:

func checkSwitch(val int) {
 switch val {
 case 0, 1:
 fmt.Println("The value is: ", val)
 }
}

与if-else相比,switch语句表达判断更清晰和简单:

package main
import (
 "fmt"
)
func checkSwitch(val int) {
 switch {
 case val < 0:
 fmt.Println("The value is less than zero.")
 case val == 0:
 fmt.Println("The value is qual to zero.")
 case val > 0:
 fmt.Println("The value is more than zero.")
 }
}
func main() {
 checkSwitch(-1)
 checkSwitch(0)
 checkSwitch(1)
}

输出结果

The value is less than zero.
The value is qual to zero.
The value is more than zero.

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