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ClassCastException in Altimer after refactoring in section 6.2

4 replies on 1 page. Most recent reply: Nov 16, 2012 8:13 AM by Eric Loots

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Shing Hing Man

Posts: 9
Nickname: 84423
Registered: Oct, 2012

ClassCastException in Altimer after refactoring in section 6.2 Posted: Nov 5, 2012 7:11 AM
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I am using Scala 2.9.2 and Akka 2.0.2.

After I have done the refactoring described in Section 6.2,
I get the following ClassCastException in Altimeter when I run Avionics:

java.lang.ClassCastException: net.sf.akka.avionics.Altimeter cannot be cast to net.sf.akka.avionics.EventSource
at net.sf.akka.avionics.Altimeter.receive(Altimeter.scala:74)
at akka.actor.Actor$class.$init$(Actor.scala:343)
at net.sf.akka.avionics.Altimeter.<init>(Altimeter.scala:21)


Line 74 in my Altimeter is
def receive = eventSourceReceive orElse altimeterReceive

I fixed the above ClassCastException by replacing

val altimeter = context.actorOf(Props[Altimeter])

with
val altimeter = context.actorOf(Props(Altimeter()))

in the class Plane.


Shing


Derek Wyatt

Posts: 64
Nickname: dwyatt
Registered: Oct, 2012

Re: ClassCastException in Altimer after refactoring in section 6.2 Posted: Nov 6, 2012 7:42 PM
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Yeah, sorry about that. I didn't include the change in the book, but we'll get it in the next release.

I would advise against using the versions you're using though... there's been a LOT of change in 2.10 and 2.1. If it's possible to upgrade, please do.

Andreas Gies

Posts: 15
Nickname: 84653
Registered: Nov, 2012

Re: ClassCastException in Altimer after refactoring in section 6.2 Posted: Nov 14, 2012 7:32 PM
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I was running into the same issue and have taken the advice to go to Scala 2.10.0-RC and akka 2.1.

Codewise I think I am now in line with what is in the book except for the Avionics class, where the Duration construction did not work in my code. Perhaps I am just missing the point. The time settings on my end are now:

implicit val timeOut = Timeout(5000);

or

system.scheduler.scheduleOnce(FiniteDuration(1, "s"))

Also, the package scala.concurrent.util.duration seems to have vanished. Perhaps thats because its a newer RC of Scala 2.10.


As a side note, I am using IntelliJ as my IDE and had everything up and running with 2.9.2 based Scala. Switching to 2.10-RC2 killed my SBT plugin and I finally reverted to maven. I think it's probably me not getting the entire picture of how things play together.

If you are interested, I can share the maven settings in case other IntelliJ users have the same problem.


Great book, btw. I really like the writing style.

Andreas

TC Chung

Posts: 1
Nickname: 84551
Registered: Nov, 2012

Re: ClassCastException in Altimer after refactoring in section 6.2 Posted: Nov 15, 2012 12:55 AM
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Use this build.sbt to get the latest versions in Scala, Akka, and ScalaTest


name := "AkkaInvestigation"

version := "0.1"

scalaVersion := "2.10.0-RC2"

resolvers += "Typesafe Repository" at "http://repo.typesafe.com/typesafe/releases/"

resolvers += "OSS Sonatype Public" at "https://oss.sonatype.org/content/groups/public/"

libraryDependencies ++= Seq(
"org.scalatest" % "scalatest_2.10.0-RC2" % "2.0.M4-B2" % "test",
"com.typesafe.akka" %% "akka-testkit" % "2.1.0-RC2" cross CrossVersion.full,
"com.typesafe.akka" %% "akka-actor" % "2.1.0-RC2" cross CrossVersion.full
)


As for the duration package, I believe it has been moved to


import scala.concurrent.duration._

Eric Loots

Posts: 4
Nickname: 84502
Registered: Nov, 2012

Re: ClassCastException in Altimer after refactoring in section 6.2 Posted: Nov 16, 2012 8:13 AM
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Thanks TC, that really helped!

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