How to insure a provider with autoDispose + family is disposed before another is initialized

[trevhud]

Describe what scenario you think is uncovered by the existing examples/articles

I have a autoDispose family future provider that is watched in a widget. When the family argument changes, the widget is rebuild with the new argument and the new instance of the provider is initialized. After that, the previous instance referenced by the previous argument is disposed. It is unclear how I would make sure that onDispose is called on the first instance before the second is created.

Describe why existing examples/articles do not cover this case

The family and autoDispose documentation does not describe this potential problem.

[rrousselGit]

What you're asking for most likely stems from a misunderstanding of what family does.

Could you explain clearly why you want this?

[trevhud]

@rrousselGit
It's that I need the previous provider to be disposed of before the current one is created. The reason is because you can only use one camera controller at a time and it must be created with the correct resolution, based on a parameter.

I understand that both can be active simultaneously and that they are independent. This makes sense and works for many use cases. But what would you suggest for when you don't want this to be the case and yet you need to pass a parameter into the provider?

[rrousselGit]

The reason is because you can only use one camera controller at a time and it must be created with the correct resolution, based on a parameter.

In this case, using family does not make sense, since family is about possibly having multiple controllers at once.

Rather, you may want something like:

final dimensionProvider = StateProvider((ref) => Size(600, 400));

final cameraControllerProvider = Provider((ref) {
  final dimension = ref.watch(dimensionProvider);

  return CameraController(dimension);
});

and when you want to change the resolution, instead do ref.read(dimensionProvider.notifier).state = Size(...);

[trevhud]

Yeah, that's how I had it initially. I was hoping to pass in the parameter so that this camera system could be fully encapsulated. That way I can use it elsewhere with completely different params. I also have to pass in the callback that needs to get called with the result of the image detection and processing. So I was hoping to not need to manage that state provider. Oh well, let me know if you happen to think of any other ideas.

[TimWhiting]

If you make the cameracontroller a ChangeNotifier or StateNotifier you can create a setter / method to change the dimensions. Also why are you using callbacks rather than Futures? The Notifier could have a method to return a future or a stream with the result of the image detection / processing.

[trevhud]

@rrousselGit I was able to refactor to use a non-family provider. However, I still have the same problem that my provider gets recreated before the previous onDispose is done running. Seems like it stems from onDispose not being able to take a future. What do you think?