Creating Map[String, Map[String, Object]] from List[Object]

Question

I'm just getting used to Scala and I have

case class Person(name: String, birthPlace: String, hairColor: String)

I know that there should be a good way to convert a List[Person] to

Map[Name, Map[Birthplace, Person]]

But, I can't quite figure out how to do it.

Any and all help would be appreciated.

just a general question: Why not store 2 separate maps (assuming multiple people can have the same birthplace)? Map[Name,List[Person]] and Map[Birthplace,List[Person]] and then resultPersonListA.intersect(resultPersonListB) ? The advantage imo is that you have direct access to both maps? — elmalto
– elmalto, Commented Jul 12, 2016 at 20:19

Dima · Accepted Answer · 2016-07-12 19:58:02Z

4

There could be more then one person with the same name and birthplace, so a better data type for this kind of thing would be Map[String, Map[String, Seq[Person]]. You can create it using .groupBy:

    list
      .groupBy(_.name)
      .mapValues(_.groupBy(_.birthplace))

If you want to ignore multiple occurrences, you can discard them by adding this at the end:

      .mapValues(_.mapValues(_.head))

answered Jul 12, 2016 at 19:58

Dima

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