i’d like to put everything in the `when` but then,...

# announcements

[nfrankel]

i’d like to put everything in the when
but then, how do i compute the id
so i can use it in the later evaluations?

[Vampire]

How about this?

val id = string?.let { Json.parse(it) }?.asObject()?.get("id")
return when {
    id == null -> null
    id.isString -> Util.entry(id.asString(), string)
    else -> Util.entry(id.asObject(), string)
}

[kenkyee]

Could do:
when (something)
No?

[Vampire]

Not in this case

[streetsofboston]

What about

when(val id =...) {
    ...
}

[Vampire]

I don't think you would win much.
This could be used to restrict the scope of id,
but the when result is directly returned, so there is nothing the id could leak into.
Besides that whyever, then id cannot be smart-casted to not-null in the second branch, but you need

return when(val id = string?.let { Json.parse(it) }?.asObject()?.get("id")) {
    id == null -> null
    id!!.isString -> Util.entry(id.asString(), string)
    else -> Util.entry(id.asObject(), string)
}

or

return when(val id = string?.let { Json.parse(it) }?.asObject()?.get("id")) {
    id == null -> null
    id?.isString -> Util.entry(id?.asString(), string)
    else -> Util.entry(id?.asObject(), string)
}

or similar.
But I think this is more a compiler bug.

[nfrankel]

thanks for your help folks 🙂

[Vampire]

Nah, it is not a compiler bug and it also cannot work

[Vampire]

if you have when(val ...) { ... } then the subject is captured as that val so that you can use it within the branches easily,
but the when expression variant would still be the one with parameter and thus you cannot use arbitrary expressions but only supplying values or ranges that are compared or checking types and as it is not is String but .isString you need the parameterless variant