I found a basic way to do this by manually passing the ClassTag. It is not
very pretty but it works:
import akka.actor._
import scala.reflect.ClassTag
class MyActor[V](size: Int, default: V, ct: ClassTag[V]) extends Actor {
// Array of given size filled with given default value
val array = Array.fill[V](size)(default)(ct)
override def receive: Receive = {
case i: Int if i < size && i >= 0 => println(array(i))
}
}
val system = ActorSystem("test")
val myActor = system.actorOf(Props(classOf[MyActor[Double]], 100, 0.0,
implicitly[ClassTag[Double]]))
myActor ! 3
// Correctly returns 0.0
On Friday, 9 October 2015 22:05:56 UTC+2, Rolf wrote:
>
> I wish to create an actor that stores an array of elements of some general
> type V. The typical way to instantiate such an array is to provide a
> ClassTag and default value. I have implemented this as follows:
>
> import akka.actor._
> import scala.reflect.ClassTag
>
> class MyActor[V : ClassTag](size: Int, default: V) extends Actor {
>
> // Array of given size filled with given default value
> val array = Array.fill[V](size)(default)
>
> override def receive: Receive = {
> case i: Int if i < size && i >= 0 => println(i)
> }
> }
>
> val system = ActorSystem("test")
> val myActor = system.actorOf(Props(classOf[MyActor[Double]], 100, 0.0))
> // java.lang.IllegalArgumentException: no matching constructor found on
> class MyActor for arguments [class java.lang.Integer, class
> java.lang.Double]
> // at akka.util.Reflect$.error$1(Reflect.scala:81)
> // ...
>
> Unfortunately, the above code does not work and I get an exception as soon
> as the actor is created. It seems that Akka does not pass the implicit
> class tag that is necessary to instantiate the class(?) Note that there is
> no problem when using the above pattern in a normal class:
>
> import scala.reflect.ClassTag
>
> class Test[V : ClassTag](size: Int, default: V) {
>
> // Array of given size filled with given default value
> val array = Array.fill[V](size)(default)
>
> }
>
> val test = new Test[Double](100, 0.0)
> test.array(3)
> // Correctly returns 0.0
>
> Any advice on how to get something like this working in Akka?
>
> Thanks!
>
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