Consider the following trait:

trait Aggregatable[Command] {

  protected[aggregator] type ActorReply

  protected[aggregator] val actorReplyClassTag: ClassTag[ActorReply]

  ... // Additional Implementation 
}

then, the following abstract class:

abstract class AsyncWorker[Request, Reply] extends Aggregatable[AsyncWorkerRequest[Request, Reply]] {

  override final type ActorReply = AsyncWorkerReply[Request, Reply]

  override protected val actorReplyClassTag: ClassTag[AsyncWorkerReply[Request, Reply]] = ???

  ... // Additional Implementation 
}

and then the concrete implementation:

class SiteCategoriesExtractorWorker extends AsyncWorker[SiteCategoriesRequest, SiteCategoriesReply]

The problem is that I cannot initialize actorReplyClassTag properly.

The desired solution should:

1. SiteCategoriesExtractorWorker should not be aware of actorReplyClassTag
2. type ActorReply is used on aggregator package as asInstanceOf[ActorReply]
3. actorReplyClassTag is used on messageAdapter (https://doc.akka.io/japi/akka/current/akka/actor/typed/scaladsl/ActorContext.html#messageAdapter(scala.Function1,scala.reflect.ClassTag)
4. Aggregatable is preferred to be a trait rather then abstract class

Note: I'm using reflection in order to make some generic aggregation over Aggregatable interface.

Any ideas how to achieve this?

CodePudding user response：

You just need to pass class tags of the parameters down to AsyncWorker, then class tag will be available implicitly:

class AsyncWorker[Request : ClassTag, Reply : ClassTag] extends Aggregatable[AsyncWorkerRequest[Request, Reply]] {
  type ActorReply = AsyncWorkerReply[Request, Reply]
  val actorReplyClassTag: ClassTag[ActorReply] = implicitly[ClassTag[ActorReply]]
}