Scala method multiple parameter groups with overload

Question

Trying to overload a method with multiple parameter groups, where the 2nd parameter type differs doesn't seem to work. This will not compile:

class Foo {
  def boo(a: String)(b: String): Unit = ()
  def boo(a: String)(b: Int): Unit = boo(a)(b.toString)
}

I would have thought that it would be compiled into boo(String, String) and boo(String,Int) methods and thus be ok in the JVM. But I guess not.

What I'm looking for is a workaround - I want to keep the parameter groups and the overloaded name so its transparent to the caller, but any other hacks are welcome.

Ben Reich · Accepted Answer · 2015-07-22 00:20:21Z

2

You could have an intermediary layer that has an overloaded apply method:

object Foo {
    def boo(a: String) = BooMaker(a)
    case class BooMaker(a: String) {
        def apply(b: String): Unit = ()
        def apply(b: Int): Unit = apply(b.toString)
    }
}

This will allow you to call Foo.boo("a")("b") or Foo.boo("a")(1), but introduces the potentially undesired intermediary tier.

answered Jul 22, 2015 at 0:20

Ben Reich

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Comments

andyczerwonka · Accepted Answer · 2015-07-21 23:32:35Z

1

Does it need to be curried? It won't compile because of the partial application. The following should compile just fine.

class Foo {
  def boo(a: String, b: String): Unit = ()
  def boo(a: String, b: Int): Unit = boo(a, b.toString)
}

If you can give more context to your actual use case, it might help with giving a better answer.

answered Jul 21, 2015 at 23:32

andyczerwonka

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1 Comment

sksamuel Over a year ago

It needs to be curried because I want the 2nd parameter group for block style invocation. It's for a DSL.

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