groovy-dsl-statemachine

In this project we show how to write complex DSL using groovy powerful features (closures, command chains, @DelegatesTo).

preface

Domain-Specific Languages are small languages, focused on a particular aspect of a software system. They allow business experts to read or write code without having to be programming experts.

project description

We provide complex and fully tested DSL for programming finite state machine:

• Grammar: immutable class representing DSL sentence:

  on transitionEvent move from fromState to toState

  which is represented in code as:

  new Grammar().on(transitionEvent).from(fromState).to(toState)
  

  or using closures:

  Grammar.make {
                  on transitionEvent, { from fromState, { to toState } }
               }
  

  Remark: note that the word order in sentence is optional, so:

  Grammar.make {
                  on transitionEvent, { from fromState, { to toState } }
               }    
  

  is basically equivalent to

  Grammar.make {
                  from _fromState, { to _toState, { on _event } }
               }
  

  and so on.

• Fsm - immutable class representing finite state machine (transitions container)

  • we create Fsm objects using FsmBuilder
  • we could load Fsm (transitions map) using closure:

    def fsm2 = Fsm.load {
        apply { on _event1, { from _state1, { to _state2 } } }
        apply { on _event2, { from _state2, { to _state3 } } }
        initialState _state0
    }        
    

    will load: _state0 as initial state and [_event1:[_state1, _state2], _event2:[_state2, _state3]] as transitions map
  • order of functions in closure is optional
  • to move from current state to the other state we call

    fsm.fire(event)
    

    Remark: if we cannot move from current state to the requested state on the given event we will stay in the current state - no exception is thrown.

tests

Coverage: 86%