Maybe I'm missing something, but shouldn't there b...

# language-proposals

[dave08]

Maybe I'm missing something, but shouldn't there be an inner object declaration? Something similar to:

class Foo {
   val num = 1

   inner class Bar {
      val one = "something $num"
   }

   val bar = Bar()

   init {
     // use it:
     println(bar.one)
   }
}

[Sam]

This actually came up not long ago: https://kotlinlang.slack.com/archives/C0B9K7EP2/p1662464968720489

[Sam]

The discussion was inconclusive 😄

[dave08]

Thanks for that reference... I see I'm not the only one that misses this! There wasn't any reaction from the Kotlin devs though... I wonder if this is really possible/or maybe against the concept of an object.

[Sam]

I did find some results on YouTrack:
• https://youtrack.jetbrains.com/issue/KT-13453/Ability-to-create-inner-objects
• https://youtrack.jetbrains.com/issue/KT-16970/inner-object

[Sam]

One was declined, the other is still open

[dave08]

Ok, well I'm the 7th thumbs up on that one... 🤷🏼‍♂️

[dave08]

Oh, on the other one there's:

The point of the current design is that a named object is always a singleton. This is not possible with inner objects, that why they are prohibited.

And using anonymous objects doesn't seem like a big problem, TBH

[dave08]

But I thought the thread before mentioned that anonymous objects don't work here...?

[dave08]

Maybe they closed that issue because the workaround doesn't work, so they might reconsider the whole proposition in the non-closed issue? Not too clear from those issues...

[elizarov]

inner object Foo { ... } is simply a confusing concept. Moreover, if you need it, you can always write:

val Foo = object { ... }

[dave08]

I tried that too... it didn't seem to work either... in the end I needed to instantiate the inner class and use that instance... which I don't really understand why it would be that different from inner object...

[dave08]

Even though a regular object is globally scoped, how could an inner object be understood as not being scoped to the current instance of the containing class? That's exactly what inner is doing... giving access to the current instance's properties.

[elizarov]

named objects are singletons.

[elizarov]

In Kotlin

[elizarov]

I might be wrong, though. Maybe it is not that confusing.

[dave08]

This pattern could be useful to be used as a container for some static values needing to be grouped in a class instance... say:

class SomeViewModel : ViewModel() {
  fun someAction1() {}
  fun someAction2() {}

  inner object Buttons {
    val button1 = ActionButton(R.string.action1, ::someAction1)
    val button2 = ActionButton(R.string.action2, ::someAction2)
  }
}

which is a simplified form of my use case...

[elizarov]

https://youtrack.jetbrains.com/issue/KT-16970/inner-object

[dave08]

Thanks!