Tweeter

Tweeter is a very minimalist "Twitter-like" application.

Tweeter is a school project (Jacques Noyé's Scala lesson) to train us to use Akka Actors. The aim of this project is to learn how to build message based app (opposite to usual memory-shared ones).

Note : information about scala and akka version are available in build.sbt.

How to test ?

To test just run fr.damienraymond.scala.tweeter.Tweeter.TestTweeter.

To do that, you can run sbt run.

Choices

How to handle more than one follows

If you asks to follow two times one person, a tweet should be shown more than once.

I have used a set data structure to avoid duplicated values. Two ActorRef from the same actor are equal, so they can be duplicated.

Separation between tweet and retweet

Conceptually a retweet is a tweet. It is easier to manage both separately especially for the display.

I have chosen to create a tweet class and a retweet class.

Usage of pattern ask

In Tweeter, we had to ask to the registry which ActorRef matches with a given name. Then registry send back an answer (message).

As this process is unique, a simple exchange of messages using ! could be enough. But, I think it's more logical to use pattern ask to keep the context.

Pattern ask return a Future. This can cause performance implications (http://doc.akka.io/docs/akka/current/scala/actors.html#Send_messages).

Are you the author of the tweet ?

I have chosen to add a flag to know whether you are the author of the tweet or not. It helps me to simplify the tweet display.

Another (best) solution would have been to spit a case class with a flag into two. Example :

// from :
case class HandleTweet(user: String, content: String, isFromMe: Boolean = false)

// to :
case class HandleYourTweet(user: String, content: String)
case class HandleTweet(user: String, content: String)

Handle thread safe calls between GUI and ViewActor

To handle thread safe calls between GUI and ViewActor I created this trait :

trait ThreadSafeRun {

  def safeRun(block: => Any) =
    javax.swing.SwingUtilities.invokeLater(() => {
      block
    })

}

I used safeRun for each call from ViewActor to the GUI.

On the other direction (GUI to ViewActor) I used message sending (!).