Example of Akka Actor Become

gistfile1.scala

import akka.actor.Actor

// defining messages -- Object = singleton, case class = DTO (sorta, generally)
object Born
case class Evolve(numberOfNeighbors: Int)
object Status

// receive is the method that handles incoming messages.
// alive: Receive and dead: Receive are defining alternative ways to respond to messages
// these will be switched on during runtime
class Cell extends Actor {

	def alive: Receive = {
		case Evolve(neighbors) => {
			if(neighbors < 2) become(dead)
			else if (neighbors > 3) become(dead)
		}
		case Status => println("alive!")
	}
	
	def dead: Receive = {
		case Evolve(neighbors) => {
			if(neighbors == 3) become(alive)
		}
		case Status => println("dead :(")
	}
	
	def receive = {
		case Born => become(alive)
		case Status => println("I am nothing...")
	}
}

object Main extends App {

	val cell = Actor.actorOf[Cell] // returns reference, very few public methods (id, start, stop, etc)
	cell.start // starts responding to messages
	
        // ! = send message ... so we are sending Status message to cell
	cell ! Status // > I am nothing ...
	cell ! Born
	cell ! Status // > alive!
	
	cell ! Evolve(4)
	cell ! Status // > dead :(
	
	cell ! Evolve(3)
	cell ! Status // alive!
	
	// async calls so being lazy and just adding thread sleep ~
	Thread.sleep(250)

	cell.stop
}

// the whole born thing kinda sucks as its an undefined state (neither alive nor dead).
// you'd want a factory to create alive or dead cells, although I think in most solutions 
// you don't want a cell class at all :)