Question

I have some objects that implement a trait. I am trying to have a val that is static and common to all of these objects. I have read that the way to do this is to use a companion object for the trait. I have used the following:

trait Test

object Test extends Test{
  val a = 1
}

object Test2 extends Test{
  def test = {
    val b = a
  }
}

However, in the line val b = a I get a “not found: value a” error. I would appreciate some help on how to fix this.

Answer 1

Members of companion objects are by default not visible to anyone, even their companion classes. So you need an explicit import:

trait Test

object Test extends Test{
  val a = 1
}

object Test2 extends Test{
  import Test._

  def test = {
    val b = a
  }
}

I don’t know if there is a nice way to do it without an import in every subclass…