pass variable number of arguments in scala (2.8) case class to parent constructor

Question

I was experimenting with variable constructor arguments for case classes in Scala, but am unable to pass them to the constructor of a case classes' parent:

abstract case class Node(val blocks: (Node => Option[Node])*)
case class Root(val elementBlocks: (Node => Option[Node])*) extends Node(elementBlocks)

the above doesn't compile... is it actually possible to do this?

possible duplicate of [How to pass List to Int* method in scala?](http://stackoverflow.com/questions/12436392/how-to-pass-list-to-int-method-in-scala) — om-nom-nom, Sep 15 '12 at 12:11
I've marked a new one question as *parent question* cause it's ask for general case, not only for case classes — om-nom-nom, Sep 15 '12 at 12:12

oxbow_lakes · Answer 1 · 2009-11-02T23:48:10.690

You need to use the :_* syntax which means "treat this sequence as a sequence"! Otherwise, your sequence of n items will be treated as a sequence of 1 item (which will be your sequence of n items).

def funcWhichTakesSeq(seq: Any*) = println(seq.length + ": " + seq)

val seq = List(1, 2, 3)
funcWhichTakesSeq(seq)      //1: Array(List(1, 2, 3)) -i.e. a Seq with one entry
funcWhichTakesSeq(seq: _*)  //3: List(1, 2, 3)

score 8 · Accepted Answer · answered Nov 02 '09 at 11:15

8

This works with 2.7:

abstract case class A(val a: String*)
case class B(val b: String*) extends A(b:_*)

Should work with 2.8.

answered Nov 02 '09 at 11:15

Thomas Jung

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Actually, case class inheritance is bound for being disallowed. – Daniel C. Sobral Nov 03 '09 at 01:17

pass variable number of arguments in scala (2.8) case class to parent constructor

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