I have a `List<Pair<A,B?>>` Is there an easy way to filter out all where `second==null` ...

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[pavel]

I have a List<Pair<A,B?>> Is there an easy way to filter out all where second==null and make the type be List<Pair<A,B>>?

[karelpeeters]

Not, you'll have to cast it.

[bezrukov]

You can try mapNotNull - convert Pair<A,B?> To Pair<A,B>?

[karelpeeters]

How to express this is still an open question for contracts: https://github.com/Kotlin/KEEP/blob/master/proposals/kotlin-contracts.md#open-questions

[pavel]

Thanks

[bezrukov]

Something like
list.mapNotNull{if (it.second != null) it.first to it.second else null}

[pavel]

nope, that didn’t work. The inferred type is still List<Pair<A,B?>>

[karelpeeters]

You need an intermediate variable, something like

list.mapNotNull {
    val second = it.second
    if (second == null) null else it.first to second
}

[bezrukov]

list.mapNotNull { (first, second) -> second?.let { first to second } }

[pavel]

ooo, nice

[pavel]

thank you