I have
val str = "abc:def"
val pattern = "(.*):.*".r
val prefix = str match {
case pattern(prefix) => prefix
case _ => ""
}
I want to avoid MatchError so if it matches I will return the match otherwise I will return "". This compiles and do extract "prefix = "abc". However I get a warning saying
Suspicious shadowing by a Variable Pattern
IDE is suggesting putting `` around pattern(`prefix`).
Is there a better way of doing this? Why is the IDE suggesting that solution.
The IDE shows the warning because you have 2 variables with the same name, I would suggest renaming the inner variable to something different:
val prefix = str match {
case pattern(pref) => pref
case _ => ""
}
The back ticks suggestion is not what you want in this case, you would use that if you wanted to match against the value of a variable (the IDE thinks you want that because prefix is the name of an existing variable).
You can rewrite it like below, using any other name for the prefix extracted from the pattern, because that value is then returned by the match and assigned to prefix
val str = "abc:def"
val pattern = "(.*):.*".r
val prefix = str match {
case pattern(aaa) => aaa
case _ => ""
}
Alternatively,
scala> val prefix = pattern.unapplySeq(str).map(_.head).getOrElse("")
prefix: String = abc
scala> val prefix = pattern.findPrefixMatchOf(str).map(_.group(1)).getOrElse("")
prefix: String = abc
Avoids inventing names.
