How would I alter a list within a list in Scala using functional programming

Question

Imagine I have a list[list[object]] and I wanted to get a list[list[object.field]]

How would i be able to do this through functional programming

as in if val list = list[list[object]] i tried

val newList = list(_)(_1.map(object.field))

but this gave me an error and I am confused

I just started functional programming and scala so there might be something completely illogical with this statement

What is list(_) supposed to mean? And what is _1 ? Once you get past these two, the compiler error message should become more informative. — Thilo
– Thilo, Commented Nov 13, 2019 at 11:07

Ivan Stanislavciuc · Accepted Answer · 2019-11-13 10:40:32Z

5

You need to use map as following

  case class Obj(field: String)
  val list = List[List[Obj]]()

  val fields: List[List[String]] = list.map(_.map(_.field))

or same as

  val fields: List[List[String]] = list.map(innerList => innerList.map(obj => obj.field))

or if you want to have a flattened list of fields

  val fields: List[String] = list.flatMap(_.map(_.field))

answered Nov 13, 2019 at 10:40

7,27517 silver badges19 bronze badges

Sign up to request clarification or add additional context in comments.

1 Answer 1