Hello! Is there a way to somehow assign variables in the left side expression of a `when` clause, to...

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[iex]

Hello! Is there a way to somehow assign variables in the left side expression of a when clause, to be used in the right side?

when {
    toFoo(line) != null -> elements.add(toFoo(line)) // reuse left side result instead?
}

[Pavlo Liapota]

In your example you try to reuse not the whole expression on the left toFoo(line) != null but just part of it tooFoo(line).

I would recommend to try to rewrite your code using different constructs.
For example, you can write

toFoo(line)?.let { elements.add(it) }

[iex]

but then I can’t use them in a when expression, no?

[sitepodmatt]

why not just do

toFoo(line).let { fooLine ->
when {
   fooLine != null -> doSomething
   else -> do2
 }
}

[sitepodmatt]

or

val fooLine = toFoo(line)
when {
  fooLine != null -> doSomething
  else -> do2
}

[iex]

@sitepodmatt the problem with that it that it forces me to always call the method

[iex]

by having it in the clause it’s evaluated only if all the previous branches didn’t match

[iex]

but I get it that it’s not possible it seems

[Pavlo Liapota]

you can use by lazy for local variable

val fooLine by lazy { toFoo(line) }

[iex]

oh that’s good, thanks!

[iex]

hm… not critical, but it would have been great if smart casting was possible. But with the lazy val it’s not possible 😕

[iex]

I mean such that the value isn’t optional on the right side anymore