implicit conversion - In Scala, how can I define a companion object for a class defined in Java?

Question

I'd like to add implicit conversions to Java classes generated by a modeling tool. So I want to add them to the companion object of those classes, so that the compiler automatically finds them. But I cannot add them in a separate file, because the companion has to be defined in the same file. Is there anything I can do about this?

Of course, I can define all my implicit conversions in another object and then bring it into scope, but this requires an extra import. Any other solution?

Answer 1

You can define your own companion object of course, which I often do in my own project-specific Predef-like arrangement. For example:

object domain {

  type TimeUnit = java.util.concurrent.TimeUnit
  object TimeUnit {
    def valueOf(s : String) = java.util.concurrent.TimeUnit.valueOf(str)
    val Millis = java.util.concurrent.TimeUnit.MILLISECONDS
    //etc
  }

Then this can be used:

import my.domain._
val tu : TimeUnit = TimeUnit.valueOf("MILLISECONDS")

But your domain.TimeUnit is a module (i.e. scala object)