Reflection Based toString

show-reflect.scala

import util.NameTransformer

def unfold[A](a: A, f: A => Option[A]): Stream[A] = {
  Stream.cons(a, f(a).map(unfold(_, f)).getOrElse(Stream.empty))
}

def get[T](f: java.lang.reflect.Field, a: AnyRef): T = {
  f.setAccessible(true)
  f.get(a).asInstanceOf[T]
}

def classAndSuperClasses(c: Class[_]): Stream[Class[_]] = unfold[Class[_]](c, (c) => Option(c.getSuperclass))

def showReflect(a: AnyRef): String = {
  val fields = classAndSuperClasses(a.getClass).flatMap(_.getDeclaredFields).filterNot(_.isSynthetic)
  fields.map((f) => NameTransformer.decode(f.getName) + "=" + get(f, a)).mkString(",")
}

// TEST
trait T {
  val t1 = "t1"
}

class Base(val foo: String, val ?? : Int) {
}

class Derived(val d: Int) extends Base("foo", 1) with T

assert(showReflect(new Derived(1)) == "t1=t1,d=1,??=1,foo=foo")