How to filter None's out of List[Option]?

scala option
Ralph picture Ralph · Apr 11, 2012 · Viewed 44.2k times · Source

If I have a List[Option[A]] in Scala, what is the idiomatic way to filter out the None values?

One way is to use the following:

val someList: List[Option[String]] = List(Some("Hello"), None, Some("Goodbye"))
someList.filter(_ != None)

Is there a more "idiomatic" way? This does seem pretty simple.

Answer

Nicolas picture Nicolas · Apr 11, 2012

If you want to get rid of the options at the same time, you can use flatten:

scala> someList.flatten
res0: List[String] = List(Hello, Goodbye)

Related questions

Check if a string is blank or doesn't exist in Scala

I have an Option[String]. I want to check if there is a string exists and if it's exists its not blank. def isBlank( input : Option[String]) : Boolean = { input.isEmpty || input.filter(_.trim.length > 0).isEmpty } Is there is a …

Read More
Scala: convert string to Int or None

I am trying to get a number out of an xml field ... <Quantity>12</Quantity> ... via Some((recipe \ "Main" \ "Quantity").text.toInt) Sometimes there may not be a value in the xml, though. The text will be "" …

Read More
Scala case class update value

I have a case class with 2 String members. I would like to update The second member later, so first I create an instance with String and None and later I load the data to the class and would like to …

Read More