how to do type constraints in kotlin? like I would...

# announcements

[Ifvwm]

how to do type constraints in kotlin? like I would like a value x only could have Int or String type?

[andylamax]

Kotlin doenst have a union type i.e. Int|String

how ever, if you want a function to take in an int or string, you can just overload the function

fun Foo(i:Int) : Bar { . . .}

fun Foo(s:String) : Bar { . . .}

If you are designing an api that should return an Int or String you have to do some extra work, i.e.

class Response<L,R>(val left:L,val right:R)

fun Foo(b:Bar):Response<Int,String> { . . .}

[Michael de Kaste]

excellent suggestion @andylamax

I'd like to add that a sealed either type has my preference

sealed class Either<out A, out B> {
    class Left<A>(val value: A): Either<A, Nothing>()
    class Right<B>(val value: B): Either<Nothing, B>()
}

so that you can do this (with an Either<String, Int> example)

when(either){
    is Left -> doWithString(either.value)
    is Right -> doWithInt(either.value)
}