Scala: creating HashMap using two Lists

Question

I have two lists in Scala:

val workersList = Worker1 :: Worker2 :: Worker3 :: Worker4 :: Nil // type List[Worker]
val workStationsList = WS1 :: WS2 :: WS3 :: WS4 :: Nil // type List[WorkStation]

A worker object has a parameter worksIn : List[WorkStation]

Knowing that Worker1 works in WS1 and WS2, Worker2 works in WS1 and WS2, Worker3 works in WS3 and WS4 and Worker4 works in WS3 and WS4 I want to get a HashMap[Worker, List[WorkStation]] that states exactly that.

It's result should be something like this:

Worker1 -> List(WS1 :: WS2 :: Nil)
Worker2 -> List(WS1 :: WS2 :: Nil)
Worker3 -> List(WS3 :: WS4 :: Nil)
Worker4 -> List(WS3 :: WS4 :: Nil)

I tried to do this, but it doesn't work:

val list = workersList.flatMap(w => workStationsList.map(ws => if(w.worksIn.contains(w)) w -> ws)).toMap[Worker, List[WorkStation]]

Does anyone know how can I do this?

Possible duplicate of In Scala, is there a way to take convert two lists into a Map? — Sean Patrick Floyd
– Sean Patrick Floyd, Commented Jun 9, 2017 at 15:49
The real problem is not how to convert the two lists into a HashMap. It's how I can get the result that I want. That answer doesn't help me in my specific problem. — J Costa
– J Costa, Commented Jun 9, 2017 at 15:52
Not sure what you need the second list for, you can simply do workersList.map(w => (w, w.worksIn)).toMap — Tzach Zohar
– Tzach Zohar, Commented Jun 9, 2017 at 15:52

Jeffrey Chung · Accepted Answer · 2017-06-09 15:57:56Z

1

val list = workersList.map(w => (w -> w.worksIn)).toMap // type Map[Worker, List[WorkStation]]

workStationList seems superfluous.

answered Jun 9, 2017 at 15:57

Jeffrey Chung

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