Observer not working when passing ObservableList to child widget

[vytautas-pranskunas-]

Hello,

recently we have discovered a bug where events were not showing on calendar date change. This bug was caused by the fact that reactivity were not triggered on filteredDates ObservableList change because it was passed down to child widget. However when I have added observable list usage at top level it started to acct as expected.

Not triggered

Observer(builder: (_) {
        return EventsDisplay(_store.filteredEvent);
      }),

Triggered:

Observer(builder: (_) {
        return _store.filteredEvent.isEmpty ? Container() : EventsDisplay(_store.filteredEvent);
      }),

Any ideas why?

[vytautas-pranskunas-]

Did not get it - why it is discussion if thats a bug? :D

[fzyzcjy]

Great. Btw next time you can use gist.github.com

[fzyzcjy]

return EventsDisplay(_store.filteredEvent); will only make it rebuild when the filteredEvent is re-assigned. On the other hand, if content within it changes and you have stored filteredEvent variable somewhere then it will not trigger rebuild.

Anyway, if you think this is a bug, please make a "minimal reproducible sample" :)

[vytautas-pranskunas-]

I need to trigger a rebuild thats a thing
I understand that @observable decorator triggers when reference changes but ObservableList should be triggered when content changes! And what i was expecting that i can pass ObservableList down to child and used Observer(builder: () => child) hoping that child internals gets re-rendered when I am adding more events.

[subzero911]

hey @vytautas-pranskunas- look at my topic #851 (comment)
I encountered the same issue, and we found a solution

[vytautas-pranskunas-]

@subzero911 thanks - that makes sense. Anyway it shold be added to docs :)

[deadsoul44]

Isn’t it due to the fact that observers are able to react to the observables only inside their immediate context? EventsDisplay widget has its own context.

[fzyzcjy]

Agree. @observable ObservableList is needed in this case. Not sure whether op misuse ObservableList instead of @observable ObservableList

[vytautas-pranskunas-]

it is @observable of @observableList

@observable
  ObservableList<Event> filteredEvent = ObservableList<Event>();

[subzero911]

EventsDisplay widget has its own context.

What if it's a widget whose context I can't access?
In my example below, I use YandexMap, which is from the third-party package. But I need to rebuild it somehow, in response to ObservableList changes.

[subzero911]

I encountered the same problem: #851
I pass ObservableList into YandexMap (it's a side package I can't edit) and mutate it with list.add(element).
Observer tells in a console that it just doesn't see any observables inside!
But if I pass Observable<List> and change the list like list.value = [...newList], Observer rebuilds it.
I consider it to be a bug. Observer should be aware of ObservableList inside.