Using find function for maps in scala

Question

I am trying to find a key in a Map, given a value. I am using the 'find' function by not able to figure out the right predicate for it:

val colors = Map(1 -> "red", 2 -> "blue")
def keyForValue(map: Map[Int, String], value: String) = {
    val bool = map.find{map.foreach{map.values(i) == value}}
        bool.key
  }

How do I iterate over the map and find the key when I know the value?

Answer 1

You use the same kind of predicate as with a List, but keep in mind you're evaluating it over (key,value) pairs, instead of just values (and getting a pair back as well!).

Simple example:

val default = (-1,"")
val value = "red"
colors.find(_._2==value).getOrElse(default)._1