Scala:返回布尔值的模式匹配的简短形式 [英] Scala: short form of pattern matching that returns Boolean

问题描述

我发现自己经常写这样的东西:

I found myself writing something like this quite often:

a match {     
  case `b` => // do stuff
  case _ => // do nothing
}

是否有更短的方法来检查某个值是否与模式匹配?我的意思是，在这种情况下，我可以只写 if (a == b)//do stuff，但是如果模式更复杂怎么办?就像在匹配列表或任意复杂性的任何模式时一样.我希望能够写出这样的东西:

Is there a shorter way to check if some value matches a pattern? I mean, in this case I could just write if (a == b) // do stuff, but what if the pattern is more complex? Like when matching against a list or any pattern of arbitrary complexity. I'd like to be able to write something like this:

if (a matches b) // do stuff

我对 Scala 比较陌生，所以请原谅，如果我遗漏了一些重要的东西:)

I'm relatively new to Scala, so please pardon, if I'm missing something big :)

推荐答案

这正是我编写这些函数的原因，这些函数显然令人印象深刻，因为没有人提到它们.

This is exactly why I wrote these functions, which are apparently impressively obscure since nobody has mentioned them.

scala> import PartialFunction._
import PartialFunction._

scala> cond("abc") { case "def" => true }
res0: Boolean = false

scala> condOpt("abc") { case x if x.length == 3 => x + x }
res1: Option[java.lang.String] = Some(abcabc)

scala> condOpt("abc") { case x if x.length == 4 => x + x }
res2: Option[java.lang.String] = None

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