[feature]: Asserting values are present when viewmodel.dataReady is true

[TjardL]

Is your feature request related to a problem? Please describe.

When using a FutureViewModel, !viewModel.dataReady is a nice helper to indicate whether the data has been loaded. When it is true, one can be sure that the values are there. However, I still need to use ! on the viewModel.data in this case, despite being sure that the data is there. This is error prone because I might use the ! in instances where the data is indeed not there.

Describe the solution you would like

I image some kind of assertion when viewModel.dataReady is true such that when viewModel.data is used under this scope, the non-null return type can be used.
For now i have written the following extension function such that i can use viewModel.safeData, but i think it might be possible to use viewModel.data, and deduce the information that the data is loaded.

import 'package:stacked/stacked.dart';

extension SafeDataAccess<T> on DataStateHelper<T> {
  /// Asserts that data is non-null if dataReady is true and returns the data.
  T get safeData {
    if (!dataReady) {
      throw StateError('Data is not ready to be accessed');
    }
    return data as T; // Since dataReady is true, data is guaranteed to be non-null.
  }
}

Additional Context

[FilledStacks]

Interesting.

I also don't like the approach of nullable data, but it's the only way (we see currently) for future to operate successfully.

I like your safeData option.

You think you can make a PR with that change in the same place where the data property is currently located?