Get all the classes that implements a trait in Scala using reflection

Question

I want to list out all the case classes which implements a particular trait. I am currently using Clapper ClassUtil for doing that. I am able to get the case classes that ar

Answer 1

Looking at the source code, the problem seems to be that it doesn't follow the interfaces hierarchy. If you do that, you find all instances:

package foo

import java.io.File

import org.clapper.classutil.{ClassFinder, ClassInfo}

object Main extends App {
  val jar     = new File("target/scala-2.11/class_test_2.11-0.1.0.jar")
  val finder  = ClassFinder(jar :: Nil)
  val classes = ClassFinder.classInfoMap(finder.getClasses().iterator)
  val impl    = find("foo.NamedEntity", classes)
  impl.foreach(println)

  def find(ancestor: String, classes: Map[String, ClassInfo]): List[ClassInfo] =
    classes.get(ancestor).fold(List.empty[ClassInfo]) { ancestorInfo =>
      val ancestorName = ancestorInfo.name

      def compare(info: ClassInfo): Boolean =
        info.name == ancestorName ||
        (info.superClassName :: info.interfaces).exists {
          n => classes.get(n).exists(compare)
        }

      val it = classes.valuesIterator
      it.filter { info => info.isConcrete && compare(info) } .toList
    }
}

Answer 2

ClassUtil now contains this functionality (v1.4.0, maybe also in earlier versions):

val finder = ClassFinder()
val impl = ClassFinder.concreteSubclasses("foo.NamedEntity", finder.getClasses())