Mapでcollect

Scalaコレクションメソッドメモ(Hishidama's Scala collection method Memo)

filterとmapを組み合わせたやつなので、こんな感じでfilterぽくかけるしmapぽくもかける。 Traversableなので、ListでもMapでもいける。

scala> val m = Map("name" -> "hoge", "currency" -> Some("USD"))
m: scala.collection.immutable.Map[String,java.io.Serializable] = Map(name -> hoge, currency -> Some(USD))

scala> m.collect { case(k, Some(v)) => k -> v}
res0: scala.collection.immutable.Map[String,Any] = Map(currency -> USD)

scala> m.collect { case(k, Some(v)) => k -> v }
res1: scala.collection.immutable.Map[String,Any] = Map(currency -> USD)

scala> m.collect { case(k, Some(v)) => k -> v.toString.length }
res5: scala.collection.immutable.Map[String,Int] = Map(currency -> 3)