Question

I need the object (or “singleton object” or “companion object”… anything but the class) defined by a string name. In other words, if I have:

package myPackage
object myObject

…then is there anything like this:

GetSingletonObjectByName("myPackage.myObject") match {
  case instance: myPackage.myObject => "instance is what I wanted"
}

Answer 1

Scala is still missing a reflection API. You can get the an instance of the companion object by loading the companion object class:

import scala.reflect._
def companion[T](implicit man: Manifest[T]) : T = 
  man.erasure.getField("MODULE$").get(man.erasure).asInstanceOf[T]


scala> companion[List$].make(3, "s")
res0: List[Any] = List(s, s, s)

To get the untyped companion object you can use the class directly:

import scala.reflect.Manifest
def companionObj[T](implicit man: Manifest[T]) = { 
  val c = Class.forName(man.erasure.getName + "$")
  c.getField("MODULE$").get(c)
}


scala> companionObj[List[Int]].asInstanceOf[List$].make(3, "s")
res0: List[Any] = List(s, s, s)

This depends on the way scala is mapped to java classes.