Extract second tuple element in list of tuples

Question

I have a Map where each value is a list of Tuples such as:

List(('a',1), ('b', 4), ('c', 3)....)

what is the most scala-thonic way to change each value is still a LIst but is only the second element of each Tuple

List(1,4,3)

I have tried

myMap.mapValues(x => x._2)

And I get

error: value _2 is not a member of List[(Char, Integer)]

any tips?

Solution 1

Try this:

    myMap.mapValues(_.map(_._2))

The value passed to mapValues is a List[(Char,Integer)], so you have to further map that to the second element of the tuple.

Solution 2

Would that work for you?

val a = List(('a',1), ('b', 4), ('c', 3))
a.map(_._2)

Solution 3

Note that mapValues() returns a view on myMap. If myMap is mutable and is modified, the corresponding changes will appear in the map returned by mapValues. If you really don't want your original map after the transformation, you may want to use map() instead of mapValues():

myMap.map(pair => (pair._1, pair._2.map(_._2)))