list - 如何修复模式匹配详尽警告？

Question

一些Scala代码:

val list = List(Some("aaa"), Some("bbb"), None, ...)

list.filter(_!=None).map {
  case Some(x) => x + "!!!"
  // I don't want to handle `None` case since they are not possible
  // case None
}

当我运行它时，编译器提示:

<console>:9: warning: match may not be exhaustive.
It would fail on the following input: None
                  list.filter(_!=None).map {
                                   ^
res0: List[String] = List(aaa!!!, bbb!!!)

如何在不提供 case None 的情况下修复该警告线？

Answer 1

如果您正在使用 map之后 filter ，您可以使用 collect .

list collect { case Some(x) => x + "!!!" }