State Management

flueco_state_management is an optional package built on Provider. It exports ViewModel, StateNotifier, ViewState, StateDataProvider, and helper APIs such as SafeZoneResultMixin and Computation. It is separate from the service-provider/container lifecycle: provide view models to widgets with Provider's widget APIs.

Model observable state

ViewState is an Equatable-based base class. Make state immutable and include all fields that determine equality; StateNotifier only notifies when the new value differs from the current value by ==.

class CounterState extends ViewState {
 final int count;

 const CounterState(this.count);

 @override
 List<Object?> get props => <Object?>[count];
}

class CounterViewModel extends ViewModel<CounterState> {
 CounterViewModel() : super(const CounterState(0));

 void increment() => setState(CounterState(state.count + 1));
}

setState is protected, so expose intent-specific methods from the view model rather than allowing widgets to replace state arbitrarily. ViewModel.read, watch, and select delegate to the configured StateDataProvider (Provider by default). Use read for one-time access/actions, watch when the widget depends on the whole model, and select when it depends on a projection.

Provide the model in the widget subtree with Provider, for example ChangeNotifierProvider(create: (_) => CounterViewModel(), child: ...). Let the provider own and dispose instances it creates. Avoid mutating a state object in place: that can make equality-based change detection miss updates.

SafeZoneResultMixin and Computation are additional helpers; consult their API when using them rather than treating them as required parts of every view model. This package is not re-exported from flueco; add it as a separate dependency. See the flueco_state_management reference for its public exports.