```fun toMap(): Map<String, Double> = mapOf(...

# getting-started

[henrik]

fun toMap(): Map<String, Double> = mapOf("key" to nullableDouble1, "key2" to nullableDouble2).filterValues { it != null }

complains that "expected Map<String, Double> but found `Map<String, Double?>`". Is there an easy way around this other than appending as Map<String, Double>?

[spand]

You can do something like .entries.mapNotNull { (k,v) -> v?.let {k to v} }.toMap()

[spand]

Unfortunately .mapValuesNotNull() does not exist

[spand]

Or rather this does not exist yet:

[spand]

https://youtrack.jetbrains.com/issue/KT-4734

[henrik]

I solved it by adding .mapValues { it.value ?: 0.0 } at the end

[henrik]

(hint from https://discuss.kotlinlang.org/t/filternotnull-for-map-values/1419 )

[karelpeeters]

Maybe .mapValues { it!! } is safer.

[henrik]

I hate having !! in kotlin code

[karelpeeters]

Then put the propesed function somewhere in your codebase. ?: 0 just hides the issue and you're back to not actually having null safety.

[karelpeeters]

You've just replaced null with 0.0.

[henrik]

yeah, but I just removed all null values in the filter statement before that

[henrik]

so that mapValues is just a dummy

[henrik]

(with a proper comment)

[karelpeeters]

Yeah, and .mapValues { it!! } is a safer dummy that will throw if someone ever changes the map call.

[henrik]

good point

[henrik]

Weirdly it's mapValues { it.value!! }

[karelpeeters]

Really?

[karelpeeters]

Double {{}}?

[henrik]

😄 nope 🙂

[henrik]

Hah, I finally figured out how to do this properly.

fun toMap(): Map<String, Double> = 
    mapOf("key" to 1.1, "key2" to null)
    .mapNotNull { it.value?.let { value -> it.key to value } }
    .toMap()