if I have a `Map<String, Thing?>` is there a...

# getting-started

[Joe]

if I have a Map<String, Thing?> is there an equivalent of Iterable#filterNoNull() that will give me a Map<String,Thing> for all non-null values?

[Shawn]

oh god

[Shawn]

how do you even have a Map<String, V?>

[Shawn]

sounds like a nightmare to work with

[Joe]

mapOf("paramString" to nullableFunction(nullableParameter)) -- yup its ugly

[Shawn]

if you want to filter out the null mappings eventually, why not perform your filter step earlier?

[Seri]

instead of using null, could you wrap that failure in a typesafe class?

[Shawn]

first thought might be to assemble a list of pairs, filterNotNull on the values, and then call toMap() on the resulting List<Pair<String, V>>

[Shawn]

serisium’s suggestion is also a good option if you have the ability to do so in this situation

[Joe]

cool, thanks, i'll see what i can wrangle together

[Seri]

something like

sealed class Thing {
  class Success: Thing()
  class Failure: Thing()
}

val map = mapOf("paramString" to NullableFunction(nullableParameter) ?: Thing.Failure())

val filteredMap = map.filter { k, v -> v is Thing.Success }

[Joe]

yeah that could work. what I'm trying to do is have an API layer that has very explicit parameters bridging to an existing more generic implementation that accepts named filters:
apiMethod(field1: Filter?, field2: Filter?, field3: Filter?) that internally calls impl(mapOf("field1" to field1, "field2" to field2, "field3" to field3)) --is there a better approach to this?

[Joe]

in the meantime changing nullableFunction to return a Pair<String,Filter> and then doing listOfNotNull(nullableFunction("field1",field1), ....).associate {it.first to it.second } seems to get what I want. thanks for the help

[Al Warren]

@Joe are you calling an api or are you creating an api?

[Joe]

Creating one