Scala Language Pattern Matching Matching Multiple Patterns At Once
Example
The | can be used to have a single case statement match against multiple inputs to yield the same result:
def f(str: String): String = str match {
case "foo" | "bar" => "Matched!"
case _ => "No match."
}
f("foo") // res0: String = Matched!
f("bar") // res1: String = Matched!
f("fubar") // res2: String = No match.
Note that while matching values this way works well, the following matching of types will cause problems:
sealed class FooBar
case class Foo(s: String) extends FooBar
case class Bar(s: String) extends FooBar
val d = Foo("Diana")
val h = Bar("Hadas")
// This matcher WILL NOT work.
def matcher(g: FooBar):String = {
g match {
case Foo(s) | Bar(s) => print(s) // Won't work: s cannot be resolved
case Foo(_) | Bar(_) => _ // Won't work: _ is an unbound placeholder
case _ => "Could not match"
}
}
If in the latter case (with _) you don't need the value of the unbound variable and just want to do something else, you're fine:
def matcher(g: FooBar):String = {
g match {
case Foo(_) | Bar(_) => "Is either Foo or Bar." // Works fine
case _ => "Could not match"
}
}
Otherwise, you are left with splitting your cases:
def matcher(g: FooBar):String = {
g match {
case Foo(s) => s
case Bar(s) => s
case _ => "Could not match"
}
}
