Scala pattern matching syntax

问题

I've been playing with scala pattern matching recently and was wondering whether there is a way to create an extractor inside of the case statement. The following code works, but you have to define the extractor first and assign it to a val:

val Extr = "(.*)".r
"test" match {
  case Extr(str) => println(str)
}

What I would like to do, or what I would like someone to confirm is impossible, is something like this:

"test" match {
  case ("(.*)".r)(str) => println(str)
}

EDIT: In case anyone from the scala team is reading this: Would it be feasible to implement this?

回答1:

Unfortunately it is not possible and I see no way to simplify your first example.

The case statement has to be followed by a Pattern. The Scala Language Specification shows the BNF of patterns in section 8.1. The grammar of patterns is quite powerful, but is really just a pattern, no method calls or constructors are allowed there.

回答2:

I had a similar problem and i solved it like this:

case x if x.matches("regex") => foo(x)

I don't know if this is exactly what you want, but it works

来源：https://stackoverflow.com/questions/6583011/scala-pattern-matching-syntax