Refactoring scala match case for list of strings - scala

Question

I have the following:
def myFunc(str: String): Something => {
str match {
case "a" | "a1" | "abc" | "qwe" | "23rs" => Something
case _ => None
}
}
The string list could be very long, I'd like to extract that to a function. I don't really know what to search for, since doing
def isSomething(str: String): Boolean => {
List("a","a1","abc","qwe","23rs").contains(str)
}
but case isSomething => Something doesn't work

Answer 1

Your str is a String hence won't match isSomething which is of Boolean type. Another issue with your sample code is that None is of Option type, so it would make more sense to have your match cases return the same type. Here's one approach using guard for the contains condition:
val list = List("a", "a1", "abc", "qwe", "23rs")
val s = "abc"
s match {
case s if list contains s => Some(s)
case _ => None
}
// res1: Option[String] = Some(abc)

Answer 2

Most of the other answers seem to cover fixing up the use of option, or moving away from pattern matching (a simple use of guards isn't really pattern matching, IMO)
I think you may be asking about extractors. If so, this might be closer to what you want:
case class Something(str: String)
// define an extractor to match our list of Strings
object MatchList {
def unapply(str: String) = {
str match {
case "a" | "a1" | "abc" | "qwe" | "23rs" => Some(str)
case _ => None
}
}
}
def myFunc(str: String): Option[Something] = {
// use our new extractor (and fix up the use of Option while we're at it)
str match {
case MatchList(str) => Some(Something(str))
case _ => None
}
}
// Couple of test cases...
myFunc("a") // Some(Something(a))
myFunc("b") // None

Answer 3

First you have used wrong => operator while defining the function.
scala> def isSomething(str: String): Boolean = {
| List("a","a1","abc","qwe","23rs").contains(str)
| }
isSomething: (str: String)Boolean
scala> def myFunc(str: String): String = {
|
| str match {
| case str if(isSomething(str)) => "Something"
| case _ => "None"
| }
| }
myFunc: (str: String)String
scala> myFunc("a")
res9: String = Something
I don't know what is something so i have treated it as a string. You could modify it according to your use case.
Hope it helps.

Answer 4

You can do something like below
val list = List("a", "a1", "abc", "qwe", "23rs")
def myFunc(str: String): Option[String] = {
list.contains(str) match {
case true => ??? //calling something function should return Some
case false => None
}
}
Option[String] can be changed according to the return type you have , but None suggests that the true case should return Option type . So String can be changed to your desired datatype