CODEWITHSUNDEEP
scala
fuzzycuffs
fuzzycuffs

Reputation: 139

Scala groupby Tuples

I have a Seq[((Tuple A),(Tuple B))]

Is there an easy way to groupby Tuple A so I get Seq[(Tuple A, Seq[Tuple B])]

I.ve tried groupby(x => x.TupleA) but it throws a Mapping Exception: Do not know how to serialize key of tuple.

Upvotes: 4

Views: 5915

Answers (1)

akuiper
akuiper

Reputation: 215117

I think this works. Use groupBy(_._1) to group your sequence by the first element of the tuple, and collect the second element of the tuples in a list:

val s = Seq(((1,2,3), (4,5,6)), ((1,2,3), (5,6,7)), ((2,3,4), (4,5,6)))

s.groupBy(_._1).mapValues(_.map(_._2))
// res1: scala.collection.immutable.Map[(Int, Int, Int),Seq[(Int, Int, Int)]] = 
//          Map((1,2,3) -> List((4,5,6), (5,6,7)), (2,3,4) -> List((4,5,6)))

If you want the result to be a list instead of Map, use toList to convert:

s.groupBy(_._1).mapValues(_.map(_._2)).toList

gives:

// List(((1,2,3),List((4,5,6), (5,6,7))), ((2,3,4),List((4,5,6))))

Upvotes: 8

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