Question

Consider this code:

class Outer {
  class Inner
}

In Java it would be possible to create an instance of Inner with:

Outer.Inner inner = new Outer().new Inner();

I know I can write this in Scala:

val outer = new Outer
val inner = new outer.Inner

But I wonder if it is possible to express the same without the assignment to outer.

Both

new Outer.new Inner  

and

new (new Outer).Inner

are not accepted by the compiler.

Is there something I’m missing?

Answer 1

First of all, I doubt that the instantiation in one go is any meaningful — you are like throwing away the Outer instance, keeping no reference to it. Makes me wonder, if you weren’t thinking of a Java static inner class, like

public class Outer() {
   public static class Inner() {}
}

which in Scala would translate to Inner being an inner class of Outer‘s companion object:

object Outer {
    class Inner
}

new Outer.Inner

If you really want an inner dependent class, and you just want more convenient syntax for instantiating it, you could add a companion object for it:

class Outer {
   object Inner {
      def apply() = new Inner()
   }
   class Inner
}

new Outer().Inner()