I've a Map where the key is a String and the value is an Int but represented as a String.
scala> val m = Map( "a" -> "1", "b" -> "2", "c" -> "3" )
m: scala.collection.immutable.Map[String,String] = Map(a -> 1, b -> 2, c -> 3)
Now I want to convert this into a Map[String, Int]
scala> m.mapValues(_.toInt)
res0: scala.collection.immutable.Map[String,Int] = Map(a -> 1, b -> 2, c -> 3)
mapValues is lazy - transforming function is applied every single time when referring to map values.As shown in Brian's answer, mapValues is the best way to do this.
You can achieve the same effect using pattern matching, which would look like this:
m.map{ case (k, v) => (k, v.toInt)}
and is useful in other situations (e.g. if you want to change the key as well).
Remember that you are pattern matching against each entry in the Map, represented as a tuple2, not against the Map as a whole.
You also have to use curly braces {} around the case statement, to keep the compiler happy.
error: illegal start of simple expression. See also stackoverflow.com/a/4387118/699224