Scala best way of turning a Collection into a Map-by-key?
dictionary, scala, scala-collections
Solution
You can use
c map (t => t.getP -> t) toMap
but be aware that this needs 2 traversals.
Problem
If I have a collection `c` of type `T` and there is a property `p` on `T` (of type `P`, say), what is the best way to do a map-by-extracting-key? ``` val c: Collection[T] val m: Map[P, T] ``` One way is the following: ``` m = new HashMap[P, T] c foreach { t => m add (t.getP, t) } ``` But now I need a mutable map. Is there a better way of doing this so that it's in 1 line and I end up with an immutable Map? (Obviously I could turn the above into a simple library utility, as I would in Java, but I suspect that in Scala there is no need)