Util to do projection on case classes

PsetUtils.scala

object TestApp extends App {
  val temp = Temp("a", "b", List(1, 2, 3, 4))
  val psetUtils: PsetUtils = new PsetUtils(classOf[Temp])
  println("line 1: " + psetUtils.toMap(temp, List("a", "c")))
  println("line 2: " + psetUtils.toMap(temp, List("a")))
  println("line 3: " + psetUtils.toMap(temp, List("b")))
  println("line 4: " + psetUtils.toMap(temp, List("c")))
  println("line 5: " + psetUtils.toMap(temp, List("c", "a", "b")))

}

/*
OUTPUT:
line 1: Map(a -> a, c -> List(1, 2, 3, 4))
line 2: Map(a -> a)
line 3: Map(b -> b)
line 4: Map(c -> List(1, 2, 3, 4))
line 5: Map(c -> List(1, 2, 3, 4), a -> a, b -> b)
*/

import scala.reflect.runtime.universe._

class PsetUtils(types: Class[_ <: Product]*) {
  private val mirror = runtimeMirror(getClass.getClassLoader)
/**
 * extract the field name from the class type and store them in Map[String, Map[String, Int]]
 * the second Int is the index of the field in the Object.
 */ 
  private val fieldsDeclaration = types.map(tg => tg.getSimpleName ->
    mirror.classSymbol(tg).toType.members
      .filter(_.isInstanceOf[MethodSymbol])
      .filter(_.asInstanceOf[MethodSymbol].isCaseAccessor).map {
      case m: MethodSymbol =>
        m.name.toString
    }.toList.reverse.zipWithIndex.toMap
  ).toMap

  /**
   * Convert the object to map with the fields you pass in. 
   */
  def toMap(obj: AnyRef, fields: List[String]): Map[String, Any] = {

    val className = obj.getClass.getSimpleName

    fieldsDeclaration.get(className) match {
      case None => Map.empty[String, Any]
      case Some(declaration) => {
        fields.map(name => {
          val fieldIndex = declaration(name)
          name -> obj.asInstanceOf[Product].productElement(fieldIndex)
        }).toMap
      }
    }
  }
}

case class Temp(a: String, b: String, c: List[Int])

can you add a bit of documentation internally to better explain your different steps?

@yairogen I add comments