(Pattern) matching against strings in Scala

Question

I want to compare a given string to a given set of other strings. Instead of using a series of ifs I went for the more concise pattern matching way, and intuitively wrote:

val s = "match"

val s1 = "not match"
val s2 = "not really a match"
val s3 = "match"

s match {
  case s1 => println("Incorrect match 1")
  case s2 => println("Incorrect match 2")
  case s3 => println("Match")
  case _ => println("Another incorrect match")
}

Which, surprisingly to me, resulted in:

Incorrect match 1

And my compiler warning that beyond case s2 =>... my code is unreachable. Why doesn't my approach work? And how can I "match" against a string?

Do you require pattern matching? – Martijn Dec 16 '17 at 12:57 — Martijn, Dec 16 '17 at 12:57
Yes, the example is simplified to bring my problem across. – parazs Dec 18 '17 at 15:34 — parazs, Dec 18 '17 at 15:34

score 3 · Accepted Answer · answered Dec 16 '17 at 13:08

This lowercase variable with pattern match in Scala, it will be thought it's a new temp variable. that's caused your code will output Incorrect match 1. so you can use an identifier to encode your variable to match their value, like:

  s match {
    case `s1` => println("Incorrect match 1")
    case `s2` => println("Incorrect match 2")
    case `s3` => println("Match")

or you can update your variable name to uppercase, like to: S1, S2, S3

(Pattern) matching against strings in Scala

1 Answers1