Bert Becker Bert Becker - 1 month ago 15
Scala Question

sbt-android: unable to use scala-reflect on android: java.rmi.Remote not found

I'm trying to use the scala-reflect package for android development.
I have added the scala-reflect dependency in my build.sbt:

libraryDependencies += "org.scala-lang" % "scala-reflect" % "2.11.8"


but I get an exception:

java.lang.NoClassDefFoundError: Failed resolution of: Ljava/rmi/Remote;
at scala.reflect.internal.Definitions$DefinitionsClass.RemoteInterfaceClass$lzycompute(Definitions.scala:370)
at scala.reflect.internal.Definitions$DefinitionsClass.RemoteInterfaceClass(Definitions.scala:370)
at scala.reflect.runtime.JavaUniverseForce$class.force(JavaUniverseForce.scala:255)
at scala.reflect.runtime.JavaUniverse.force(JavaUniverse.scala:16)
at scala.reflect.runtime.JavaUniverse.init(JavaUniverse.scala:147)
at scala.reflect.runtime.JavaUniverse.<init>(JavaUniverse.scala:78)
at scala.reflect.runtime.package$.universe$lzycompute(package.scala:17)
at scala.reflect.runtime.package$.universe(package.scala:17)


I have tried to add the java source of
java.rmi.Remote
and
java.rmi.RemoteException
and built the project with
android:package --core-library
(because sbt has not found the dexCoreLibrary option) , it builded successfully, but I got the runtime error.

So, is it possible to add the java.rmi dependency otherwise, that scala.reflect can use it?

I uses the scala.reflect library in the context of an implementation of a method Option.orDefault:

class RichOption[+A : TypeTag](val delegate: Option[A]) {

def orDefault : A = delegate.getOrElse {
delegate match {
case t if typeOf[A] <:< typeOf[Int] => 0.asInstanceOf
case _ => throw new IllegalAccessException("there is no default value for this type.")
}
}


}


If you know a better implementation for Option.orDefault
(possibly without scala.reflect), please let me know.

Answer

Much better:

case class Default[A](value: A)
object Default {
  implicit val intDefault: Default[Int] = Default(0)
  // other Default implementations
}

class RichOption[+A](val delegate: Option[A])(implicit d: Default[A]) {
  def orDefault : A = delegate.getOrElse(d.value)
}

You get a compilation error instead of a runtime error if used with a type which doesn't have a defined default value, no complex matching, no need for a large dependency, etc.