Is it/will it be possible to have `external value class Whatever(whatever: String)` ?

# javascript

[Joost Klitsie]

Is it/will it be possible to have external value class Whatever(whatever: String) ?

[andylamax]

I think it is kind of dificult, coz the kotlin compiler won't know how to inline external declarations. What are you trying to achieve? What is your usecase?

[Joost Klitsie]

I wish to pass ids to a props object

[Joost Klitsie]

like:

external interface SomeProps: RProps {
    var someId: SomeId
}

Where someId is:

data class SomeId(val uuid: UUID)

[Joost Klitsie]

it would be perfect to transform this SomeId to a value class, but with inline classes this was not possible

[Joost Klitsie]

so I wonder, did anything change with value classes or not

[andylamax]

why is

external interface SomeProps: RProps {
    var someId: UUID
}

not working for you?

[Joost Klitsie]

that would work, but I would love to have type safety

[Joost Klitsie]

Because I can pass different types of ids to the same props

[Joost Klitsie]

I first used UUIDs which led to bugs and I refactored to wrap the uuid so they are strongly typed

[Joost Klitsie]

a very good use case for value classes

[Joost Klitsie]

but doesn't work with external classes/interfaces

[andylamax]

I still believe you can achieve type safety without using value classes

[Joost Klitsie]

yeah I use data classes

[Joost Klitsie]

but the value classes are more optimized

[andylamax]

I get your point know

[andylamax]

does the compiler throw an error when you change SomeId into a value class?

[andylamax]

not external value class, just a value class

[Joost Klitsie]

I did not try it out to be honest 🙂 Maybe over the weekend I create a test project with kotlin 1.5 to see what happens