Filter a collection of objects by values of a specific object field

CollectionUtils.scala

package utils

import scala.collection.generic.CanBuildFrom
import scala.collection.{SeqLike, mutable}

/**
 * Created by Lior Gonnen on 8/17/14.
 */
object CollectionUtils {

    implicit class ExtendedSeqLike[A, Repr](seqLike : SeqLike[A, Repr]) {

        /**
         * Returns a new collection with distinct objects in relation to the function f<br/>
         * Used mainly to get filter objects based on a distinct onject field
         * 
         * @example
         * case class Person(name : String, age : Int)<br/>
         * val people = List(Person("Joe", 28), Person("Jennifer", 35), Person("Jane", 22))<br/>
         * val filtered = people.distinctBy(_.age < 30)<br/>
         * 
         * @param f     A function that maps object to the desired unique representation
         * @param cbf   Implicit factory builder
         * @tparam B    The type of the returned collection
         * @return      A new collection with distinct objects in relation to f
         */
        def distinctBy[B](f : A => B)(implicit cbf : CanBuildFrom[Repr, A, Repr]) : Repr = {
            val builder = cbf(seqLike.repr)
            val seen = mutable.HashSet[B]()
            for (x <- seqLike) {
                val fx = f(x)
                if (!seen(fx)) {
                    builder += x
                    seen += fx
                }
            }
            builder.result()
        }
    }
}