is there a cleaner way to do this? ```val filtered...

# announcements

[Nikky]

is there a cleaner way to do this?

val filteredMap: Map<String, B> = someMap.filterValues { value -> value is B } as Map<String, B>

because the unchecked cast is marked as warning

[nanodeath]

not sure. I'd probably just make my own filterValuesInstanceOf method and suppress it there.

[Nir]

Depends what you mean by cleanly

[Nir]

You could just add another step where you do the downcast after filtering

[Nir]

Instead of casting the collection

[Nir]

That's obviously adding work though

[Nir]

You could do it in a single step it looks like using mapNotNullTo, but it's a bit awkward

[Nir]

Another option is to write your own associateNotNull, it's not in the standard library unfortunately. With that function it would be easy

[Nir]

Writing it is also pretty easy

[Nikky]

i eneded up doing these:

inline fun <K, reified RV> Map<K, *>.filterValueIsInstance(): Map<K, RV> {
    @OptIn(ExperimentalStdlibApi::class)
    return buildMap {
        [e-mail](this)
    }
}

inline fun <reified RK: K, reified RV: V, K, V, C : MutableMap<in RK, in RV>> Map<K, V>.filterIstInstance(destination: C): C {
    for ((key, value) in this) if (key is RK && value is RV) destination.put(key, value)
    return destination
}

inline fun <reified RV: V, K, V, C : MutableMap<K, in RV>> Map<K, *>.filterValueIsInstanceTo(destination: C): C {
    for ((key, value) in this) if (value is RV) destination.put(key, value)
    return destination
}

inline fun <reified RK: K, K, V, C : MutableMap<in RK, V>> Map<*, V>.filterKeyIsInstance(destination: C): C {
    for ((key, value) in this) if (key is RK) destination.put(key, value)
    return destination
}

[Nikky]

i guess for completions sake i will add a few more like that

[Vampire]

One way would be

val filteredMap: Map<String, B> = someMap.mapNotNull { (key, value) -> if (value is B) key to value else null }.toMap()