Matching against a regular expression in Scala

Question

I fairly frequently match strings against regular expressions. In Java:

java.util.regex.Pattern.compile(\"\\w+\").matcher(\"this_is\").matches

Ouch. Scala has

Answer 1

I created a little "Pimp my Library" pattern for that problem. Maybe it'll help you out.

import util.matching.Regex

object RegexUtils {
  class RichRegex(self: Regex) {
    def =~(s: String) = self.pattern.matcher(s).matches
  }
  implicit def regexToRichRegex(r: Regex) = new RichRegex(r)
}

Example of use

scala> import RegexUtils._
scala> """\w+""".r =~ "foo"
res12: Boolean = true

Answer 2

I usually use

val regex = "...".r
if (regex.findFirstIn(text).isDefined) ...

but I think that is pretty awkward.

Answer 3

Currently (Aug 2014, Scala 2.11) @David's reply tells the norm.

However, it seems the r."..." string interpolator may be on its way to help with this. See How to pattern match using regular expression in Scala?

Answer 4

You can define a pattern like this :

scala> val Email = """(\w+)@([\w\.]+)""".r

findFirstIn will return Some[String] if it matches or else None.

scala> Email.findFirstIn("test@example.com")
res1: Option[String] = Some(test@example.com)

scala> Email.findFirstIn("test")
rest2: Option[String] = None

You could even extract :

scala> val Email(name, domain) = "test@example.com"
name: String = test
domain: String = example.com

Finally, you can also use conventional String.matches method (and even recycle the previously defined Email Regexp :

scala> "david@example.com".matches(Email.toString)
res6: Boolean = true

Hope this will help.