Question

It looks like there’s some magic translation between Java data structures when accessing them from JRuby; they appear to work like plain ruby maps and arrays. However, Scala data structures don’t. I found surprisingly little when googling around for JRuby / Scala interop. How would you, for instance, iterate over Scala’s Map and List types?

Answer 1

Sure you can. But it’s a bit of hoop-jumping. For lists:

require "/usr/share/scala/lib/scala-library.jar" # load the scala lib
Java::scala.collection.immutable::List.empty.send("::", 1)
  .map(lambda{|e|e+1},
        Java::scala.collection.immutable.List.canBuildFrom) # by lopex

Now you have a scala list in jruby. You could write some nice Ruby API filling in the implicits for you.