CODEWITHSUNDEEP
scala
Alan Coromano
Alan Coromano

Reputation: 26008

No ClassTag available for T -- not for Array

Here is a part of code involving akka:

abstract class AkkaBaseClass[T <: AkkaClass1, U <: Loger] extends Actor {

  protected val val1 = context.actorOf(Props[T])
  protected val val2 = context.actorOf(Props[U])

  def receive = {
    case "test" => {
      implicit val timeout = Timeout(Config.timeout seconds)
      val future = val1 ? "request"
      val result = Await.result(future, timeout.duration).asInstanceOf[List[ActorRef]]
      sender ! result
    }


    case "log" => val2 ! "log"
  }

class AkkaClass1 extends Actor { .... }


trait Loger extends Actor { ..... }

There are 2 errors:

No ClassTag available for T and No ClassTag available for U

But T and U are not arrays. What do I do about that?

Upvotes: 2

Views: 3605

Answers (2)

Viktor Klang
Viktor Klang

Reputation: 26579

Please do not block on Futures if not required:

Here's a solution to your problem.

abstract class AkkaBaseClass[T <: AkkaClass1 : ClassTag, U <: Loger : ClassTag] extends Actor {

  protected val val1 = context.actorOf(Props[T])
  protected val val2 = context.actorOf(Props[U])

  def receive = {
    case "test" => val1 forward "request"
    case  "log" => val2 ! "log"
  }

class AkkaClass1 extends Actor { .... }


trait Loger extends Actor { ..... }

Upvotes: 3

Daniel C. Sobral
Daniel C. Sobral

Reputation: 297155

Though you omitted the place where the errors took place, I'm guessing they are happening at Props. It is probably the case that Props take an implicit ClassTag as a parameter, particularly since it doesn't take any other parameter. And though a ClassTag is used by array creation, it can also be used for other things, such as getting a Class that can then be used to instantiate classes by reflection, or as a reference when comparing instances received.

To solve it, declare AkkaBaseClass like this:

import scala.reflect.ClassTag

abstract class AkkaBaseClass[T <: AkkaClass1 : ClassTag, U <: Loger : ClassTag] extends Actor {

Upvotes: 8

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