英文:
Do Go switch/cases fallthrough or not?
问题
当你到达Go语言中的一个case的结尾时，会发生什么？它会继续执行下一个case吗？还是默认情况下大多数应用程序都不希望继续执行下去？
英文:
What happens when you reach the end of a Go case, does it fall through to the next, or assume that most applications don't want to fall through?
答案1
得分: 144
不，Go的switch语句不会自动执行下一个case。如果你希望执行下一个case，必须显式地使用fallthrough语句。根据规范：
在case或default子句中，最后一个非空语句可以是一个（可能带标签的）"fallthrough"语句，以指示控制流从该子句的末尾流向下一个子句的第一个语句。否则，控制流将流向switch语句的末尾。"fallthrough"语句可以出现在表达式switch的除最后一个子句外的所有子句的最后一条语句中。
例如（很抱歉，我实在想不出一个真实的例子）：
switch 1 {
case 1:
fmt.Println("我会打印")
fallthrough
case 0:
fmt.Println("我也会打印")
}
输出：
我会打印
我也会打印
你可以在这里查看示例代码：https://play.golang.org/p/va6R8Oj02z
英文:
No, Go switch statements do not fall through automatically. If you do want it to fall through, you must explicitly use a fallthrough statement. From the spec:
> In a case or default clause, the last non-empty statement may be a
> (possibly labeled) "fallthrough" statement to indicate that control
> should flow from the end of this clause to the first statement of the next clause. Otherwise control flows to the end of the "switch"
> statement. A "fallthrough" statement may appear as the last statement of all but the last clause of an expression switch.
For example (sorry, I could not for the life of me think of a real example):
switch 1 {
case 1:
fmt.Println("I will print")
fallthrough
case 0:
fmt.Println("I will also print")
}
Outputs:
I will print
I will also print
答案2
得分: 18
保留了break作为默认选项，但不再使用fallthrough。如果你想要在匹配到一个case后继续执行下一个case，你应该明确地使用fallthrough关键字。
switch choice {
case "optionone":
// 一些指令
fallthrough // 控制流将不会从这个case中跳出，而是继续执行下一个case
case "optiontwo":
// 一些指令
default:
return
}
英文:
Break is kept as a default but not fallthrough. If you want to get onto the next case for a match, you should explicitly mention fallthrough.
switch choice {
case "optionone":
// some instructions
fallthrough // control will not come out from this case but will go to next case.
case "optiontwo":
// some instructions
default:
return
}
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