Scala: Remove none elements from map and flatten

Question

I have a map:

Map(\"key1\" -> Some(\"value1\"), \"key2\" -> None, \"key3\" -> Some(\"value3\"))

I want to remove all None

Answer 1

My take using pattern matching is:

Map("key1" -> Some("value1"), "key2" -> None, "key3" -> Some("value3")).collect {
  case (key, Some(value)) => key -> value
}
// Map(key1 -> value1, key3 -> value3)

Collect acts like combined map + filter

Answer 2

Using partition over the map, like this,

val (flattened,_) = map.partition(_._2.isDefined)

Answer 3

You can use for-comprehension + pattern-matching:

for((k, Some(v)) <- yourMap) yield k -> v

Answer 4

My take using for comprehensions:

val m = Map("key1" -> Some("value1"), "key2" -> None, "key3" -> Some("value3"))
for( (key,value) <- m if(value.isDefined)) yield (key,value.get)