is there a way to do a computation inside a `when`...

# announcements

[nfrankel]

is there a way to do a computation inside a when block?

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

here, i first check a if then compute the id then execute my when using the computed id
it feels not as readable as it could

[Animesh Sahu]

Maybe this feels ok?

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)
}

[Animesh Sahu]

Welp, nevermind the syntax is only for sth like switch statements (matches with elements instead), it won't allow condition checks.

[nfrankel]

no worries
thanks for the try

[Milan Hruban]

I like this (might need minor corrections to be compilable)

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

also, if isString didn't return Boolean? but rather Boolean, I would do

val id = string?.let(Json::parse)?.asObject()?.get("id") ?: return null
    return if(id.isString) Util.entry(id.asString(), string) else Util.entry(id.asObject(), string)

[nfrankel]

thanks @Milan Hruban
i’ll try how it looks in intellij

[Milan Hruban]

let me know if it worked, so I can learn too:)

[nfrankel]

good news: code works
on the readability side, i’m less happy