About

Scala state machine

Features

• fluent builder for state machine setup
• comprehensive error message when setup is incomplete or faulty, e. g.

Invalid state machine:
    initial state is not defined
    transition config
        direct transition
            target is not defined
            source is not defined
            event is not defined

• transitions
  • direct transition - from state A to state B
  • choice transition - from state A to state B if guard == true, otherwise to state C
• state listener
• transition action
• transition error action
• unit tests

Example

+------+     +------+     +------+
|  S1  |     |  S2  |     |  S3  |
|      |     |      |     |      |
|      |     |      |     |      |
|      +-E1-->      +-E4-->      |
+---+--+     +------+     +--^---+
    |                        |
    +-----------E2-----------+

val stateMachine = StateMachineBuilder()
            .initialState("S1")
            .configureTransitions()
                .withTransition()
                    .source("S1")
                    .target("S2")
                    .event("E1")
                .and()
                .withTransition()
                    .source("S2")
                    .target("S3")
                    .event("E4")
                .and()
                .withTransition()
                    .source("S1")
                    .target("S3")
                    .event("E2")
                .end()
            .build()
            
stateMachine.sendEvent("E1")