Scala正则表达式模式匹配问题

Question

In the snippet below, part matches just fine, but part2 fails to match.

val part = """TEXT:123:4:5"""
val part2 = """ text="TEXT:123:4:1">"""
val regex = """TEXT:(\d+):(\d+):(\d+)""".r

def matchAndPrint(text: String) {
  println(text match {
    case regex(num1, num2, num3) => s"$num1:$num2:$num3"
    case _ => "no match"
  })
}
matchAndPrint(part)
matchAndPrint(part2)

I'm not sure how to fix it. Any advice?

Answer 1

That's what unanchored is for, as shown here .

scala> val part = """TEXT:123:4:5"""
part: String = TEXT:123:4:5

scala> val part2 = """ text="TEXT:123:4:1">"""
part2: String = " text="TEXT:123:4:1">"

scala> val regex = """TEXT:(\d+):(\d+):(\d+)""".r.unanchored
regex: scala.util.matching.UnanchoredRegex = TEXT:(\d+):(\d+):(\d+)

scala> def matchAndPrint(text: String) {
     |   println(text match {
     |     case regex(num1, num2, num3) => s"$num1:$num2:$num3"
     |     case _ => "no match"
     |   })
     | }
matchAndPrint: (text: String)Unit

scala> matchAndPrint(part)
123:4:5

scala> matchAndPrint(part2)
123:4:1

Sorry I couldn't find a canonical Q&A. It has come up several times.

Answer 2

Regex matching requires that it match the full string, so the text before and after the relevant portion in part2 is causing you the problem.

Try this:

val regex = """.*TEXT:(\d+):(\d+):(\d+).*""".r

""" text="TEXT:123:4:1">""" match {
  case regex(num1, num2, num3) => s"$num1:$num2:$num3"
}

// res0: String = 123:4:1

Answer 3

You are trying to do a complete match.

You therefore need to allow for the characters at the start and end of part2 , for example:

val regex = """.*TEXT:(\d+):(\d+):(\d+).*""".r

(Just adding .* at the start and end of the regex, to match anything)