Extension delegating property should work

# getting-started

[orangy]

Extension delegating property should work

[Hullaballoonatic]

so a property that delegates an extension? i didn't know that was a thing. can that be used to dynamically implement interfaces on instantiating a class?

[gcx11]

@Hullaballoonatic https://kotlinlang.org/docs/reference/extensions.html#extension-properties

[Hullaballoonatic]

thanks!

[Hullaballoonatic]

i can't do delagation since i want to point to an interface property. not sure how extension property helps me here

[Hullaballoonatic]

i have an interface with a property called scalingProperty and i want to be able to implement this interface but allowing to name the property as something with context, like volume

[Hullaballoonatic]

am i overcomplicating this? is that as easy as

var volume: Volume
    get() = scalingProperty
    set(v) {
        scalingProperty = v
    }

[orangy]

yes, but var YourInterface.volume : Volume and the rest is as you wrote

[orangy]

You want to invoke it instance.volume, right?

[Hullaballoonatic]

yes

[Hullaballoonatic]

i think i had it backwards

[Hullaballoonatic]

interface Liquid<T: ItemData> : Scale<Volume, T> {
    override var scalingProperty: Volume
        get() = volume
        set(value) {
            volume = value
        }
    
    var volume: Volume
}

[orangy]

That would work too, of course, but I would make scalingProperty final, so that it wouldn’t be overriden further in hierarchy

[Hullaballoonatic]

can't implement final in interface

[orangy]

Ok, let me open an IDE 🙂

[orangy]

So, I was thinking along the lines that anything with Volume should have property `volume`:

interface Scale<TUnit, TData> {
    var scalingProperty: TUnit
}

interface Volume
object Barrel : Volume

var <TData> Scale<Volume, TData>.volume
    get() = scalingProperty
    set(value) {
        scalingProperty = value
    }

fun test(some: Scale<String, Int>, liquid: Scale<Volume, Int>) {
    some.volume = Barrel // error
    liquid.volume = Barrel // ok
}

[Hullaballoonatic]

do you know if it is possible to dynamically implement varying interfaces on a class during instantiation?

[orangy]

Like object : Volume {}?

[orangy]

Kotlin is statically typed language, so no dynamic subtyping

[Hullaballoonatic]

ah, shucks

[orangy]

Nope, that rulz metal