How do I propagate data to initial state of DataState?

[oyanyev]

Let say I have hierarchical SM and some data is passed to some inner state. I would like this data propagated to initial state on such inner state.

    @Test
    fun propagate_data_to_initial_state() {

        class MoveEvent(override val data: Int) : DataEvent<Int>
        
        val outer = DefaultState("state_initial_1")
        val inner = DefaultDataState("inner_state", defaultData = 0, dataExtractor = defaultDataExtractor())
        val innerInitial = DefaultDataState("inner_initial", defaultData = 0, dataExtractor = defaultDataExtractor())
        
        val sm = createStateMachine {
            addInitialState(outer) {
                initialState("outer_initial")
                addState(inner) {
                    addInitialState(innerInitial)
                }
                dataTransition<MoveEvent, Int> {
                    targetState = inner
                }
            }
        }
        
        sm.processEvent(MoveEvent(99))
        
        assert(inner.data == 99)
        assert(innerInitial.data == 99)
    }

[nsk90]

Hello, there is not such functionality like Data propagation, sorry. DataState/DataEvent are designed to be type safe API for passing data from event to its target state. Such propagation is out of their scope.

I suggest simply access innerInitial parent's data via direct reference to inner or parent property.

    "activeStates() not include nested machines states1" {

        class MoveEvent(override val data: Int) : DataEvent<Int>

        val outer = DefaultState("state_initial_1")
        val inner = defaultDataState("inner_state", defaultData = 0) // you can use this helper function
        val innerInitial = DefaultState("inner_initial")

        val sm = createStateMachine {
            addInitialState(outer) {
                initialState("outer_initial")
                addState(inner) {
                    addInitialState(innerInitial) {
                        onEntry {
                            check((parent as DataState<Int>).data == 99)
                        }
                    }
                }
                dataTransition<MoveEvent, Int> {
                    targetState = inner
                }
            }
        }

        sm.processEvent(MoveEvent(99))

        assert(inner.data == 99)
        assert((innerInitial.parent as DataState<Int>).data == 99)
    }

If you need more control on how this data should be stored, you should subclass DefaultState and mange the data field manually.

[oyanyev]

I want to renew the discussion, because i find such propagation necessary.
And I found also that such propagation does exist in form of propagation of TransitionParams:
setCurrentState(initialState, transitionParams)
But in DefaultDataState onDoEnter(transitionParams: TransitionParams<*>) a check happens:

if (this == transitionParams.direction.targetState) {
...
}

which returns false and data is not propagated to initial state.
Please think about changing TransitionParams.direction.targetState to match initial state before
setCurrentState(initialState, transitionParams)
to allow data smoothly propagated to initial state.

Alternatively, DataState.defaultData can be lambda and so can lazily be returned as { parent.data } in DefaultDataState onDoEnter()

else { // implicit activation
            _data = lastData
        }

lastData initialization

    override val lastData: D
        get() = checkNotNull(_lastData ?: defaultData()) {
            "Last data is not available yet in $this, and default data not provided"
        }

[oyanyev]

Sorry, I see that, in spite state is finished, transitions are triggered from within. Checked that with a test. Let's how it works in a code