Scala immutable objects and traits with val fields

Question

I would like to construct my domain model using immutable objects only. But I also want to use traits with val fields and move some functionality to traits. Please look at the f

Answer 1

This should do what you are looking for:

trait Request[T <: Request[T]] extends Cloneable {
  this: T =>
  private var rets = 0
  def retries = rets
  def incRetries:T = {
    val x = super.clone().asInstanceOf[T]
    x.rets = rets + 1
    x
  }
}

Then you can use it like

case class Download(packageName:String) extends Request[Download]
val d = Download("Test")
println(d.retries) //Prints 0
val d2 = d.incRetries
println(d2.retries) //Prints 1
println(d.retries) //Still prints 0