Generic reflective case class instantiation with Scala 2.10.x

ReflectionHelpersSnippet.scala

package test

import scala.reflect.runtime.universe._

object ReflectionHelpers extends ReflectionHelpers

trait ReflectionHelpers {

  protected val classLoaderMirror = runtimeMirror(getClass.getClassLoader)

  /**
    * Encapsulates functionality to reflectively invoke the constructor
    * for a given case class type `T`.
    *
    * @tparam T the type of the case class this factory builds
    */
  class CaseClassFactory[T: TypeTag] {

    val tpe = typeOf[T]
    val classSymbol = tpe.typeSymbol.asClass

    if (!(tpe <:< typeOf[Product] && classSymbol.isCaseClass))
      throw new IllegalArgumentException(
        "CaseClassFactory only applies to case classes!"
      )

    val classMirror = classLoaderMirror reflectClass classSymbol

    val constructorSymbol = tpe.declaration(nme.CONSTRUCTOR)

    val defaultConstructor =
      if (constructorSymbol.isMethod) constructorSymbol.asMethod
      else {
        val ctors = constructorSymbol.asTerm.alternatives
        ctors.map { _.asMethod }.find { _.isPrimaryConstructor }.get
      }

    val constructorMethod = classMirror reflectConstructor defaultConstructor

    /**
      * Attempts to create a new instance of the specified type by calling the
      * constructor method with the supplied arguments.
      *
      * @param args the arguments to supply to the constructor method
      */
    def buildWith(args: Seq[_]): T = constructorMethod(args: _*).asInstanceOf[T]

  }
}

//////////////////////////////////////////////////////////////////////////////
// USAGE
//////////////////////////////////////////////////////////////////////////////

case class Person(name: String, age: Int)
val personFactory = new ReflectionHelpers.CaseClassFactory[Person]
val result: Person = personFactory.buildWith(Seq("Connor", 27))
val expected = Person("Connor", 27)
assert(result == expected)

Person is a class, not a String