Several case classes with the same behavior in Scala

Question

I define some case classes based on Exception with identical behavior (source)

case class Foo(msg: String) extends Exception {
    override def toString: String = scala.runtime.ScalaRunTime._toString(this)
}
case class Bar(msg: String) extends Exception {
    override def toString: String = scala.runtime.ScalaRunTime._toString(this)
}
case class Boo(msg: String) extends Exception {
    override def toString: String = scala.runtime.ScalaRunTime._toString(this)
}

All these new exceptions repeat same code. I want to rid of redundant code duplication. I unsuccessfully tried to use interim common base class and traits. Please, help me remove excess code duplication.

Mario Galic Mario Galic · Accepted Answer · 2020-04-26T23:26:06

ScalaRunTime._toString takes a Product argument

def _toString(x: Product): String =
  x.productIterator.mkString(x.productPrefix + "(", ",", ")")

hence try defining

trait ProductException extends Exception with Product {
  override def toString: String = scala.runtime.ScalaRunTime._toString(this)
}

and then

case class Foo(msg: String) extends ProductException
Foo("Live long and prosper")
// res1: Foo = Foo(Live long and prosper)

This works because case classes are implicitly Products, for example, defnining

case class Foo(msg: String)

is expanded by compiler to something like

case class Foo(msg: String) extends Object with Product with Serializable

Several case classes with the same behavior in Scala

1 Answers