Question

Consider this code

val map = new HashMap[(String, String), Set[(String, Int, Double, Int)]] 
        with MultiMap[(String, String),     (String, Int, Double, Int)]

Is there a way to use the Multimap trait without repeating the type parameters definition?

Answer 1

You can use a type alias to cut down on repetition

type K = (String, String)
type V = (String, Int, Double, Int)

Then your map becomes

val map = new HashMap[K, Set[V]] with MultiMap[K, V]

However, as a stylistic rule I don’t find it a good idea to use the TupleN traits so much in code for a few reasons:

• they are harder to refactor (e.g. if you need an extra field)
• it is less obvious what they represent

Considering that the overhead of creating a bespoke class is as little as:

case class K(p1: String, p2: String)

it’s usually worth it!