list - Scala模式匹配: How to match on an element inside a list?

Question

是否可以使用Scala模式匹配来重写以下代码？

val ls: List[String] = ??? // some list of strings

val res = if (ls.contains("foo")) FOO
     else if (ls.contains("bar")) BAR
     else SOMETHING_ELSE

Answer 1

您可以使用类似的功能来实现

def onContains[T](xs: Seq[String], actionMappings: (String, T)*): Option[T] = {
  actionMappings collectFirst {
    case (str, v) if xs contains str => v
  }
}

并像这样使用它:

val x = onContains(items,
  "foo" -> FOO,
  "bar" -> BAR
)