Go中的switch fallthrough

 

 

• Go基础

switch sExpr {
case expr1:
    some instructions
case expr2:
    some other instructions
case expr3:
    some other instructions
default:
    other code
}

sExpr和expr1、expr2、expr3的类型必须一致。Go的switch非常灵活，表达式不必是常量或整数，执行的过程从上至下，直到找到匹配项；而如果switch没有表达式，它会匹配true。 Go里面switch默认相当于每个case最后带有break，匹配成功后不会自动向下执行其他case，而是跳出整个switch, 但是可以使用fallthrough强制执行后面的case代码。

http://play.golang.org/p/LySjbnt53q

package main

import "fmt"

func main() {

    switch {
    case false:
            fmt.Println("The integer was <= 4")
            fallthrough
    case true:
            fmt.Println("The integer was <= 5")
            fallthrough
    case false:
            fmt.Println("The integer was <= 6")
            fallthrough
    case true:
            fmt.Println("The integer was <= 7")
    case false:
            fmt.Println("The integer was <= 8")
            fallthrough
    default:
            fmt.Println("default case")
    }
}

运行结果：

The integer was <= 5

The integer was <= 6

The integer was <= 7

从本例可以看出：switch人第一个expr为true的case开始执行，如果case带有fallthrough，程序会继续执行下一条case,不会再判断下一条case的expr,如果之后的case都有fallthrough,default出会被执行。