Scala Pattern matching multiple outputs - scala

Question

i am new to scala and got stuck with one pattern matching case.
i am writing a pattern match as below,
case class data(record:String)
def x(input:String)= input match {
case "a" => val a = data("a")
case "b" => val b = data("b")
case anythingElse = val others = ...other object creation
}
i would like to access the variables val a,val b and val others outside of the def x.
is there a way to return val a, val b and val others once the calls to the def x is completed.

Answer 1

Your understanding of pattern matching is not entirely correct, you can assign vals in each case area, but the only purpose of that would be to do something temporary. In scala whatever statement you place last is the return value. This cannot be a val assignment statement, or no value (aka unit) would be returned
def x(input:String)= input match {
case "a" => data("a and something special")
case "b" =>
val temp = "b"+" Hello"
data(temp)
case other => data(other)
}

Answer 2

To my understanding, you are trying to define a new variable in a scope that is outside of each case block:
case class data(record:String)
def x(input:String)= input match {
case "a" => val a = data("a")
case "b" => val b = data("b")
case anythingElse = val others = ...other object creation
}
x("a")
println(a) // should print data("a")
Correct?
That is not going to work! Because Scala "Cannot resolve symbol a". It wasn't defined in the scope where you are using it.
Instead you could propagate it to outer scope using some kind of a data container ( defined in the outer scope ). It could be an array, a variable, or a Map. However this will also make it a mutable container. Not recommended.
A better approach would be to actually return your state from x() method and then use that state. Something like this:
case class Data(record: String)
val template: Map[String, Option[Data]] = List("a", "b", "c").map(_ -> None).toMap[String, Option[Data]]
def x(input: String): Map[String, Option[Data]] = input match {
case "a" => template + ("a" -> Some(Data("a")))
case "b" => template + ("b" -> Some(Data("b")))
case anythingElse => template + ("others" -> Some(Data("others")))
}
val returnMap = x("a")
for (x <- returnMap("a")) {
println(x)
}
OUTPUT:
Data(a)

Answer 3

Values a, b and others are local to each case; consider though
def x(input:String)= input match {
case "a" => (Some(data("a")), None, None)
case "b" => (None, data("b"), None)
case anythingElse = (None, None, `...other object creation`)
}
where the function returns a triplet of Option in which a None represents no matching, and Some(data("...")) a match; hence for instance
val (a,b,others) = x("a")
delivers
a = Some(data("a"))
b = None
others = None