Type safe props

[britter]

Apply akka best practices: Introduce props methods in the companion objects of Actors for creating Props in a type safe manner.

[britter]

This is currently WIP. I'm trying to implement this for the creation of reports in the AppActor as well, but I need some time refactor the map function which maps from reporter configs to ActorRefs.

[britter]

I'm working on type safe creation of Reporter actors. Here's what I've got so far in the AppActor:

  val reporters = config.reporters.map(config2Actor)

  def config2Actor(entry: (String, AbstractReporterConfig)): (String, ActorRef) = {
    val consoleReporterClass = classOf[ConsoleReporter]
    val slackReporterClass = classOf[SlackReporter]

    val props = entry._2.implementation match {
      case consoleReporterClass => Props(new ConsoleReporter(mapper, config.asInstanceOf[ConsoleReporterConfig]))
      case slackReporterClass => Props(new SlackReporter(mapper, config.asInstanceOf[SlackReporterConfig]))
    }

    val actor = context.actorOf(props, s"reporter-${entry._1}")
    (entry._1, actor)
  }

This looks pretty ugly. A few things that could be improved:

• move ReporterConfiguration class to the file where the reporter actor is defined
• define ReporterConfiguration implementation class in the companion object of the configuration
• define props in the companion object of the reporter actor

This would change the above implementation to:

  val reporters = config.reporters.map(config2Actor)

  def config2Actor(entry: (String, AbstractReporterConfig)): (String, ActorRef) = {
       val props = entry._2.implementation match {
      case ConsoleReporterConfiguration.implementation => ConsoleReporter.props(mapper, config.asInstanceOf[ConsoleReporterConfig])
      case SlackReporterConfiguration.implementation => SlackReporter.props(mapper, config.asInstanceOf[SlackReporterConfig])
    }

    val actor = context.actorOf(props, s"reporter-${entry._1}")
    (entry._1, actor)
  }

Pros:

• uses best practice when defining props
• makes explicit which actors are created
• compile time safety when refactoring reporter actor constructor parameters

Cons:

• everything has to be written down explicitly
• feels like unnecessary boilerplate code
• you have to remember to add a case statement to config2Actor when introducing a new reporter implementation

I'd like to hear comments before I go further down this road.

[bripkens]

The second solution looks very good to me. Unnecessary boilerplate seems okay to me, especially since the addition of reporters isn't something that is going to happen very often :+1:

[hseeberger]

I don't have the time to dive into the details, but the asInstanceOf absolutely must disappear: there must be a way to use pattern matching more elegantly. Can't you define a fixed set of possible reporters (in config: foo, bar, baz) and create a corresponding ADT (sealed base trait and case objects/classes)?

[britter]

@bripkens voilà! This is ready for reintegration. Please review.

[hseeberger]

Great stuff!

[bripkens]

Cool stuff, thanks @britter! :)

[bripkens]

Also thank you @hseeberger for your comments :)