将scala（2.8）case类中的可变数量的参数传递给父构造函数

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?

Answer 1

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)

Answer 2

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.