Is there any way to create a named object using a ...

# getting-started

[Emil Kantis]

Is there any way to create a named object using a function that returns an anonymous object?

fun <T> bar() = object : Bar<T> {
  // ..
}

object Foo = bar<Int>()

[Youssef Shoaib [MOD]]

I don't think so, but you can at least place it in a `val`:

val Foo = bar<Int>()

[ephemient]

this would also be close but not quite the same

object Foo : Bar<T> by bar()

[Emil Kantis]

In my case, Bar<T> is an abstract class from a library, so delegation is a no-go.

And I need to reference it by Foo::class , again due to working with this library, so a simple val won't do 😞

[ephemient]

then if https://youtrack.jetbrains.com/issue/KT-30915/Inline-constructors were implemented and you used that instead of bar() then perhaps, but for now no.

[Emil Kantis]

Thanks for the confirmation. Not sure how the inline constructors would help, but I starred and upvoted those issues. 🙂

[ephemient]

assuming you could define constructors externally, since they'd be inlined into the caller anyway…

[ephemient]

well it's a wishful thought anyhow. I'm not sure the language will evolve in that way

[Wout Werkman]

It depends on the use case. If the program is truly safe, there is a good chance that you can get away with Nothing. Let's take the example of Java's Collections.emptyList() for example.
Practically, what Java has here is the following:

object EmptyList: List<Any?> { ... }
object Collections {
    fun <T> emptyList() = EmptyList as List<T> // This code is not safe!
}

functionThatTakesListOfInt(EmptyList) // Compiler error
functionThatTakesListOfInt(Collections.emptyList()) // Java's workaround

Luckily, in Kotlin you have Nothing, because List is covariant on T (annoying smart people words for T being out T).

So you can simply declare:

object EmptyList: List<Nothing> { ... }
functionThatTakesListOfInt(EmptyList) // Yay, works!

So if your Bar<T> is abstract class Bar<out T>, then you might be able to make it typesafe as object Foo: Bar<Nothing>() { ... }

[Youssef Shoaib [MOD]]

@Wout Werkman I think you might've posted this in the wrong thread lol!