Is there a way to create an anonymous inline/value object? Use case in :thread:.

# language-evolution

[Klitos Kyriacou]

Is there a way to create an anonymous inline/value object? Use case in 🧵.

[Klitos Kyriacou]

I have a use case for a local variable that must always be incremented every time it is accessed. I thought about making it a value class:

@JvmInline
value class SelfIncrementingLong(private var value: Long) {
    fun getAndIncrement() = value++
}
...
val offset = SelfIncrementingLong(0)

Now the only way I can get the value is using getAndIncrement.

This need is very specific and local to this function, so I didn't want to create a new class for it. It's much more concise to use an anonymous class:

val offset = object {
    private var value: Long = 0
    fun getAndIncrement() = value++
}

But now offset is boxed. Is it possible to write an anonymous object but have it as a @JvmInline value class? If not, is there an existing proposal for such a thing?

[Youssef Shoaib [MOD]]

local value classes seem to be explicitly forbidden right now, so that'd include anonymous value classes as well.

[Youssef Shoaib [MOD]]

Btw, you might wanna add an inline fun SelfIncrementingLong.getValue which calls getAndIncrement

[Youssef Shoaib [MOD]]

Oh and also, your code doesn't even compile right now because value classes must have a val, not a var. I think sadly you'll have to wait until copying functions come into the language

[Klitos Kyriacou]

Thanks. What would be the advantage of an inline fun SelfIncrementingLong.getValue?

[Youssef Shoaib [MOD]]

So you'd just do val offset by SelfIncrementingLong(0) and every time offset is used, the long would be incremented