Listening to specific updates on StateNotifier from other stateNotifiers and/or Providers

[mihael998]

Hi, I have been struggling with something for a while.
Here's what I'm trying to accomplish:

In my application I have different providers, simple ones, and also StateNotifier ones.
A lot of my StateNotifiers manage operations on lists (like add, remove, update) and so on.
In my app I have two State Notifiers with their providers like so:

class FirstNotifier
    extends StateNotifier<FirstState> {

  ArchitectureCanvasNotifier( FirstState state)
      : super(state);

  updateStateInformation(){
    state=...
  }
}

final firstNotifierProvider= StateNotifierProvider<FirstNotifier, FirstState>(
  (ref) {
    final notifier = FirstNotifier(
      FirstState(),
    );

    return notifier;
  },
);

class SecondNotifier
    extends StateNotifier<List<Model>> {

  ArchitectureCanvasNotifier( List<Model> state)
      : super(state);

  removeElement(){
    state=[...state.value!]..removeWhere(...)
  }
}

final secondNotifierProvider= StateNotifierProvider<SecondNotifier, List<Model>>(
  (ref) {
    final notifier = SecondNotifier(
      [],
    );

    return notifier;
  },
);

What I'm trying to accomplish is to update the FirstNotifier whenever removeElement is called on the second notifier.

To do so what are my options?
I could call updateStateInformation inside removeElement by passing a reference of ref to the SecondNotifier. From what I have understood there is nothing wrong in passing the ref object.
What I'm trying to reach though is an "Event" like process. I would like to put the logic of "listening" to removeElement in the FirstNotifier or FirstNotifierProvider.
So something like:

final firstNotifierProvider= StateNotifierProvider<FirstNotifier, FirstState>(
  (ref) {
    final notifier = FirstNotifier(
      FirstState(),
    );

    ref.listen<List<Model>>(secondNotifierProvider,(old,new){
      
    });
    return notifier;
  },
);

The problem is this: how can I listen to specific changes? Inside the listen callback I only have a reference to the new List. Do I have to "compute" manually the changes based on old and new value or there is a way to know that removeElement has been called?

[rrousselGit]

Your reasoning is correct.

What you're looking for (an event mechanism for every StateNotifier method) does not exist. Placing the logic within the removeElement method by passing ref like you've mentioned would be the correct solution

[mihael998]

🥲😭
Thank you for the quick response!
By using some kind of reactive pattern (for example stream with streamProvider) would it be possible, or better would it be a "recommended" way to do it? (I could look into it but I suppose you may have a "ready answer" based on your experience in discussing RiverPod things 😁)