[MVI] intent(MviView::intent) does't fire before view is attached

My question is somehow similar to this #242 So I have an intent in my view implemented like this:

override fun selectDateIntent(): Observable<Day> {
       return selectDatePubSub.distinctUntilChanged()
               .startWith(selectedDate)
               .doOnNext {
                       //this fires one time correctly because off startWith()
               }
   }

In the presenter I have this observable wrapped in the intent() function like this:

timetableInteractor.setSelectDateIntent(intent(TimetableView::selectDateIntent)} )

After debugging I noticed that the observable resulting from the wrapped intent does not emit nothing before the view is attached. So, if I add a delay to the intent implementation in the view, everything goes as expected. However, in the MVI sample code having Observable.just(object) is a recurring practice for the intent implementations, so I am curious to know what I’m doing incorrectly.

Thanks, Diogo

[kusraevs]

Binding intents actually starts in attachView method of MviBasePresenter. In MviActivity this method calls in onStart. So if you use PublishSubject item could be emitted before this time because it is a hot observable. If you use Observable.just(…) we don’t have this problem. In this situation i use BehaviorSubject instead of PublishSubject.

But if you call startWith inside intent() function it should work ok. So this is issue is the same as #242 as far as i concern

[sockeqwe]

I will work on that next week

jhowens89 [e-mail] schrieb am Fr., 23. Feb. 2018, 01:51:

@sockeqwe https://github.com/sockeqwe Did you ever come to a conclusion about #242 https://github.com/sockeqwe/mosby/issues/242? I was still very new to RxJava back then and I’d like to think the code I write down is less problematic, but I can still replicate this issue.

class MatchPlayRoundSelectorPresenter @Inject constructor(val interactor: MatchPlayRoundSelectorInteractor) : MviBasePresenter<MatchPlayRoundSelectorView, MatchPlayRoundSelectorViewState>() { override fun bindIntents() { val loadMatchPlayRoundSelectorDataIntent = intent(MatchPlayRoundSelectorView::connectDataIntent) .doOnNext { Timber.e(“TESTING_BEFORE 1”) } .switchMap { interactor.loadMatchPlayRoundSelectorData() } .doOnNext { Timber.e(“TESTING_BEFORE 2”) } .subscribeOn(Schedulers.io()) .doOnError { Timber.e(it,“Fatal error occurred”) }

    val selectNewRoundIntent = intent(MatchPlayRoundSelectorView::selectNewRoundIntent)
            .map { (round, page) -> interactor.newRoundSelected(round, page) }

    val initialState = interactor.getInitialState()

    val allIntents = Observable.merge(loadMatchPlayRoundSelectorDataIntent, selectNewRoundIntent)
            .observeOn(AndroidSchedulers.mainThread())

    subscribeViewState(allIntents.scan(initialState, ::viewStateReducer)
            .distinctUntilChanged(), MatchPlayRoundSelectorView::render)}

}

The other side of the equation looks like:

override fun connectDataIntent(): Observable<Unit> = Observable.just(Unit)//.doOnNext { Timber.e(“TESTING_BEFORE 0”) }

If I run this code, I’ll get the following relevant logs: 02-22 17:46:12.605 7068-7068/com.tour.pgatour E/MatchPlayRoundSelectorL: TESTING_BEFORE render com.tour.pgatour.match_play.leaderboard.match_play_round_selector.MatchPlayRoundSelectorViewState$WithoutData@7830fd3

If all I do is uncomment that doOnNext:

02-22 17:44:57.205 6216-6216/com.tour.pgatour E/MatchPlayRoundSelectorL: TESTING_BEFORE render com.tour.pgatour.match_play.leaderboard.match_play_round_selector.MatchPlayRoundSelectorViewState$WithoutData@fb867e3 02-22 17:44:57.206 6216-6216/com.tour.pgatour E/MatchPlayRoundSelectorL: TESTING_BEFORE 0 02-22 17:44:57.206 6216-6216/com.tour.pgatour E/MatchPlayRoundSelectorP: TESTING_BEFORE 1 02-22 17:44:57.368 6216-6216/com.tour.pgatour E/MatchPlayRoundSelectorP: TESTING_BEFORE 2 02-22 17:44:58.099 6216-6216/com.tour.pgatour E/MatchPlayRoundSelectorL: TESTING_BEFORE render WithData(viewData=MatchPlayRoundSelectorViewData(roundPlayTabs=[RoundTab(config=TabConfig(text=Round 1, backgroundColor=-16777216, textColor=-1, selectedBackgroundColor=-1, selectedTextColor=-16777216), option=com.tour.pgatour.shared_rel…

It’s like I’m so close to the boundary of the race condition that even a log will push it over. Thoughts?

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