Return value of Function Scala

Question

I have following program in Scala :

object Ch4 {

        def main(args: Array[String]) {
      println("Hello, world!")
      val x = sortMap()
      println(x)
    }                                             //> main: (args: Array[String])Unit

    def sortMap ( ) {
        val scores = scala.collection.immutable.SortedMap ( "Alice" -> 10, "Fred" -> 7, "Bob" -> 3)
        return scores
    }                                             //> sortMap: ()Unit
}

I am confused why sortMap function has return type Unit inspite of Map. Also why nothing is getting print in main function.

After changing it, I am getting this error "method sortMap has return statement; needs result type" — neel
– neel, Commented Jun 29, 2015 at 11:31
Error is removed but still nothing is getting printed in main function in Scala worksheet — neel
– neel, Commented Jun 29, 2015 at 11:34
Well, then add a return type or do not use the return statement, as suggested by the error. Frankly, you could perhaps read at least some basic tutorial or introduction on Scala before seeking help. — Suma
– Suma, Commented Jun 29, 2015 at 11:34

Lee · Accepted Answer · 2015-06-29 11:34:33Z

1

Method definitions of the form def name() { ... } implicitly return Unit. You need to add the return type and add an =:

def sortMap(): SortedMap[String, Int] = {
    val scores = scala.collection.immutable.SortedMap ( "Alice" -> 10, "Fred" -> 7, "Bob" -> 3)
    return scores
}

or simply:

def sortMap() = SortedMap("Alice" -> 10, "Fred" -> 7, "Bob" -> 3)

answered Jun 29, 2015 at 11:34

Lee

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2 Comments

neel Over a year ago

What I read in documentation is that we don't have to tell the return type of functions in Scala. Only for recursive functions return type is compulsory. Then why is it necessary here?

Lee Over a year ago

@neel - It's because you're using an explicit return, see this question. Explicit returns are rarely needed in scala.

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