Scala Reactive Programming

Case object Switch

The following code snippet shows how to use ActorContext's become() and unbecome() functions:

class MyFSMActor extends Actor { 
  def receive = { 
    case Switch => 
      become({ 
        case Switch => 
          unbecome()  
      })  
  } 
} 

Here, when SwapActor receives a switch message for first time, it changes its state to become. Then, if it receives the same message the next time, it moves to the unbecoming state.

Akka has a decent FSM DSL (Domain Specific Language) API to ease the development of FST Machines.