Hi there! Is there a way to update a `value` in `StateFlow<Map<Id, T>>`, so that current...

# coroutines

[ubu]

Hi there! Is there a way to update a value in StateFlow<Map<Id, T>>, so that current subscriber does not a receive this update? I have a particular use case from UI programming.

Suppose that this T is String. We have a list of texts, that is rendered first in a text editor. This text is then edited by our user and we receive onTextChanged(id, text) event. We now need to sync this text change with our state: map[id] = text, but we do not need to render this state again, because UI already has it.

Or maybe there is no way to resolve this problem with StateFlow ?

[zak.taccardi]

the problem you are describing is that the UI toolkit on Android updates itself

[ubu]

yes, changes are in text widget before they are in a view model.

[zak.taccardi]

my recommended solution is to not use StateFlow<String> for EditText, and let the EditText itself be the source of truth. If the ViewModel needs to update the EditText, then it should emit these updates as a “side effect”

[ubu]

it is the source of truth when text changes, indeed. but i need to work with the objet that represents state of this text in my view model; what i need is a way to have mutual syncing…

[Zach Klippenstein (he/him) [MOD]]

This can be a complicated problem, but if you’re not dealing with asynchronous updates, you can just compare the new string from your state with the current text in the view and only set it if it’s different.

[ubu]

I’m dealing also with spans, focus and diff util 🙂

[Zach Klippenstein (he/him) [MOD]]

Spans & focus can be handled by calling Editable.replace instead of setText to update the text.

[Zach Klippenstein (he/him) [MOD]]

Diffutil should be fine, unless you’re running it on a separate thread – that’s where it gets complicated.

[zak.taccardi]

Probably pretty important to run Diffutil on a separate thread

[Zach Klippenstein (he/him) [MOD]]

You can make it work, but you basically need to synchronize two concurrent state machines which is fun.