Scala inherit parameterized constructor

Question

I have an abstract base class with several optional parameters:

abstract case class Hypothesis(
    requirement: Boolean = false,
    onlyDays:   Seq[Int] = Nil,         


        

Answer 1

In my mind the policy of default values doesn't belong in the base class but should go on the concrete classes. I'd instead do the following:

trait Hypothesis {
  def requirement: Boolean
  def onlyDays: Seq[Int]
  /* other common attributes as necessary */
}

case class SomeHypothesis(anotherArg: SomeType,
                          requirement: Boolean = false,
                          onlyDays: Seq[Int] = Nil)
  extends Hypothesis

The case class fields of SomeHypothesis will fulfill the requirements of the Hypothesis trait.

As others have said, you can still use an extractor for pattern matching on the common parts:

object Hypothesis {
  def unapply(h: Hypothesis): (Boolean, Seq[Int]) = (h.requirement, h.onlyDays)
}