Hi. If I have a sub-class that sets a different companion object from its parent class, can a method on the parent class access the companion object of the current sub-class? Here's some code:

open class TheCompanion(val foo: String)

open class Parent {
    fun doIt(): String {
        return foo
    }

    companion object : TheCompanion("the-parent")
}

class Child1() : Parent() {}

class Child2() : Parent() {
    companion object : TheCompanion("child2")
}

Child1().doIt()
Child2().doIt()

How can I get

Child2().doIt()

to output

"child2"

instead of

"the-parent"

? I guess this isn't possible because there's no way to enforce that subclasses of

Parent

must have a companion object implementing a given interface, right?

I guess this isn’t possible because there’s no way to enforce that subclasses of Parent must have a companion object implementing a given interface, right?

yes

👍 thanks

spent a few minutes messing around in a scratch file, depending on what your requirements are for this hierarchy this may or may not be useful to you:

interface HasFoo {
  val foo: String
}

interface PrintsFoo : HasFoo {
  fun printFoo(): Unit = println(foo)
}

class LeafA : PrintsFoo by Companion {
  companion object : PrintsFoo {
    override val foo = "LeafA"
  }
}

class LeafB : PrintsFoo, HasFoo by Companion {
  override fun printFoo() {
    println("foo: $foo")
  }

  companion object : HasFoo {
    override val foo = "LeafB"
  }
}

LeafA().printFoo()
LeafB().printFoo()