CODEWITHSUNDEEP
scalatraitsmixins
Luke De Feo
Luke De Feo

Reputation: 2175

Make existing classes implement traits in scala

I have a class that takes key value pairs, this can come in the form a of a map object or a case class for example. Lets define the following abstraction:

 trait Reportable {
    def getAttributes : Map[String,Any]
  }

I want to have a method that takes a List[Reportable]. The possible implementations for reportable are:

The issue is i cannot figure out how to make Product (the base class of of all case classes) and the Map class implement my trait. I want to be able to take an existing class and mix in a the reportable trait, implementing it in terms of the methods the class already has.

Upvotes: 3

Views: 1361

Answers (1)

Sascha Kolberg
Sascha Kolberg

Reputation: 7162

You cannot mix a trait in like that, I think.

However, imho, sounds like a case for the EnrichMyLibrary Pattern. Example for Map:

trait Reportable {
  def getAttributes : Map[String,Any]
}

object Reportable {
  implicit class MapReportableOps(private val underlying: Map[String, Any]) extends Reportable {
    def getAttributes: Map[String, Any] = underlying
  }
}

Usage:

val reportables: List[Reportable] = Map("foo" -> "bar") :: Nil

The compiler should find the implicit wrapper class MapReportableOps for the map wherever a Reportable is expected and create a Reportable.

Upvotes: 8

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