I’m probably asking this in the wrong channel, but I’m not sure what the right one is. The question is, how do you extend an abstract inner class in Kotlin? This is legal Java:

class Outer {
  abstract class Inner {
  }
}
class Child extends Outer.Inner {
  Child(Outer outer) {
    // Calls Inner constructor, providing
    // outer as the containing instance
    outer.super();
  }
}

I can’t find an equivalent in Kotlin, if I want

Child

to live in a separate file / module. The auto converter generates this, which doesn’t compile:

class Outer {
  abstract inner class Inner
}

class Child(outer: Outer?) : Inner()

1) I had no idea you could do that in Java 🤯 2) I don’t think it’s possible, because constructor “super” calls are implicit, as part of the constructor declaration (not a procedural statement within the constructor body with some level of dynamic behavior to it) 3) You should structure your classes to be composed rather than inherited, which makes the relationship between

Inner

,

Outer

, and

Child

more explicit understandable. You can use the

with

scoping function within

Inner

to make it access members of

Outer

in a similar way to an inner class

I understand that this is an anti pattern. I’m in a situation where my hands are tied.

You can do this in Kotlin if you do not attach the

inner

qualifier on your kotlin inner class, this means it will not have direct access to parent methods/properties, but will compile

class Outer {
    abstract class Inner
}

class Child(outer: Outer) : Outer.Inner() {

    init {
        // Do work with outer if need be
    }
}

Well, yes, but that’s not what I asked.

I guess I misunderstood, my fault