Is there a function to create a `Comparable` from a `Comparator` ? If there is none, I think it woul...

# stdlib

[CLOVIS]

Is there a function to create a Comparable from a Comparator ? If there is none, I think it would be a nice addition, to make this possible:

class Foo(…) : Comparable<Foo> by fooComparator.asComparable() {

    companion object {
        private val fooComparator = compareBy({…}, {…}) // use the stdlib convenience functions for comparators
    }
}

Otherwise, it's not possible to reuse these convenience functions

[Riccardo Lippolis]

I don't see a way to do this cleanly with delegation, but reusing the convenience function is still possible by simply implementing the interface like this:

override fun compareTo(other: Foo): Int = fooComparator.compare(this, other)

Regarding delegation, I think the issue here is that the compare method in the Comparable interface needs access to the instance of Foo, and I doubt there's a way to access that in a delegate (but maybe I'm mistaken).

If comparing by a single property, something like this works:

class Foo(val x: Int): Comparable<Int> by x

but that won't work when comparing multiple properties 🙂