I'm trying to do something like this: ```val list = listOf(1,2,3,4,5) when (list) { all { it &lt...

# announcements

[mzgreen]

I'm trying to do something like this:

val list = listOf(1,2,3,4,5)
when (list) {
    all { it < 10 } -> foo()
    any { it % 2 == 0 } -> bar()
    else -> baz()
}

but it doesn't seem to be possible and I'm not sure why.

[Tobias Suchalla]

'when' does not put its argument into scope. It is (as of yet) only meant for type checks:

when(result) {
    is Success -> println("yeah!")
    else -> println("oh no!")
}

You can however use when without an argument:

when {
    list.all { it < 10 } -> foo()
    list.any { it % 2 == 0 } -> bar()
    else -> baz()
}

(I hope I got the terminology somewhat right 😬)

[Vadim Kapustin]

And 'when' matches its argument against all branches sequentially until some branch condition is satisfied. So if you expect 'foo' and 'bar' to work, then you need to do something like this:

with(list) {
    var noMatch = true
    if (all { it < 10 }) {
        foo()
        noMatch = false
    }
    if (any { it % 2 == 0 }) {
        bar()
        noMatch = false
    }
    if (noMatch) baz()
}

[mzgreen]

makes sense now, thanks!
what do you mean by saying that it doesn't put its argument into scope yet? Are there plans to change it? Do you have a tracking ticket link or something?

[Ruckus]

There are a number of open issues / proposals to augment the functionality of when. See this one for example (as well as its related isssues): https://youtrack.jetbrains.com/issue/KT-28359