#state-machine

Overview These will be notes I write to myself regarding the software necessary to program the navigation, movement, observation, orientation and battery charge control of this tumbling robotic rover. I’ll be building a state machine that represents command & control of the bot. If you’re not familiar with a state machine it’s essentially a flow chart. The flow between the ovals (conditions /…

Case for State Machines:

Adding a lot of datetime or boolean fields in the db, especially when they depend on each other.

Lot of boolean logic in the model.

Key Vocabulary:

State

Event

Transition

Migration:

Column called 'state' in the table

In the model, add a call to state_machine

Steps:

Run specs

Do some basic reading

Whiteboard the objectives & goals

Examine, Observe & Study all involved parts

A lot of tiny steps

Observe what is already done in great detail

Flow:

Go over what is already done, couple times & know the terminology

Run the specs

Fix the failing specs

Start coding after all green

Run specs

Fix code

Initialization

Initialized automatically to the initial state

Useful Methods:

private delegate IEnumerator individualStateHandler(); private Dictionary<characterStates, individualStateHandler> stateHandlers; void Awake () { changeState(characterStates.idle); stateHandlers = new Dictionary<characterStates, individualStateHandler>(); stateHandlers.Add(characterStates.idle, processIdleTransition); stateHandlers.Add(characterStates.running , processRunningTransition); stateHandlers.Add(characterStates.sprinting, processSprintingTransition); stateHandlers.Add(characterStates.jumping, processJumpingTransition); stateHandlers.Add(characterStates.falling, processFallingTransition); stateHandlers.Add(characterStates.walling, processWallingTransition); stateHandlers.Add(characterStates.wallJumping, processWallJumpingTransition); stateHandlers.Add(characterStates.lookingUpIdle, processLookingUpIdleTransition); } void Start() { StartCoroutine(stateHandlers[currentState]()); }

Where, my idle Coroutine, for example, consists of:

IEnumerator processIdleTransition() { playIfNotPlaying("Idle"); do { if (checkFallAndChangeState()) break; if (checkJumpAndChangeState()) break; if (rightKeptPressed || leftKeptPressed) { if (sprintKeptPressed ) { changeState(characterStates.sprinting); } else { changeState(characterStates.running); } break; } if (checkLookingUpAndChangeState()) break; yield return new WaitForEndOfFrame(); } while (currentState == characterStates.idle); yield return new WaitForEndOfFrame(); StartCoroutine(stateHandlers[currentState]()); }

That way, I "Start" my state machine operation on the Start() function, and after that, I always have one Coroutine corresponding to the current state running. If the current state changes, the Coroutine of the old state stops running and I start another Coroutine for the new state.