Auxiliary Constructor in Scala with multiple parameters

Question

I have a class that is initialized with an integer and a set. I want to create an auxiliary constructor that takes an integer and multiple parameters. These multiple parameters should be the contents of the set.

I need help calling the primary constructor with suitable arguments.

final class Soccer[A](max: Int, collection_num: Set[A]) {

///Auxiliary Constructor
/// new Soccer(n,A,B,C)` is equivalent to `new Soccer(n,Set(A,B,C))`.
///This constructor requires at least two candidates in order to avoid ambiguities with the
/// primary constructor.

def this(max: Int, first: A, second: A, other: A*) = {
///I need help calling the primary constructor with suitable arguments.
}

}

new Soccer(n,A,B,C)should be equivalent tonew Soccer(n,Set(A,B,C))

Why have first and second at all? Just use `elements: A*`. – Luis Miguel Mejía Suárez Sep 20 '19 at 19:50 — Luis Miguel Mejía Suárez, Sep 20 '19 at 19:50

score 2 · Answer 1 · answered Sep 20 '19 at 19:19

Try defining factory apply method on the companion object instead of auxiliary constructor like so

object Soccer {
  def apply[A](max: Int, first: A, second: A, other: A*): Soccer[A] = {
    new Soccer(max, Set[A](first, second) ++ other.toSet)
  }
}

Now construct Soccer like so

Soccer(n,A,B,C)

score 1 · Answer 2 · answered Sep 22 '19 at 07:31

Using the apply method in companion object is a good way to achieve the requirement, but if you really want to do it in auxiliary constructor, you just call the this method like:

final class Soccer[A](max: Int, collection_num: Set[A]) {
  def this(max: Int, first: A, second: A, other: A*) = {
    this(max, Set[A](first, second) ++ other.toSet)
  }
}

Auxiliary Constructor in Scala with multiple parameters

2 Answers2