Some utilities to make work with a neat_state package in Flutter more convenient
Usage
Place NeatProvider somewhere at the top of a widget tree of your app (onChangeCallback is optional, can be useful to log state transitions):
@override
Widget build(BuildContext context) {
return NeatProvider<AppState>(
initialState: const AppState(),
onChangeCallback: (Change<AppState> change) {
debugPrint('NeatState: ${change.currentState} => ${change.nextState}');
},
child: MaterialApp(
title: 'Flutter Neat State Demo',
theme: ThemeData(primarySwatch: Colors.blue),
home: const MyHomePage(title: 'Flutter Neat State Demo Home Page'),
),
);
}
Update your widget (with optional buildWhen condition) on state change with BlocBuilder from flutter_bloc package:
@override
Widget build(BuildContext context) {
return BlocBuilder<NeatState<AppState>, AppState>(
buildWhen: (AppState previous, AppState current) => current.counter != previous.counter,
builder: (BuildContext context, AppState state) {
return Text(
'${state.counter}',
style: Theme.of(context).textTheme.headline4,
);
},
);
}
Update your state anywhere in the widget tree using context extensions:
void _incrementCounterByContextExtension(BuildContext context) {
// A state update function, takes an old state as an argument and must return the new state
context.neatUpdate<AppState>(
(AppState state) => state.copyWith(
// return the new state that is copy of an old state..
counter: state.counter + 1, // ..with incremented counter
),
);
}
Or by using reference to NeatState:
// Get NeatState reference from context with Provider
final NeatState<AppState> neatState = context.read<NeatState<AppState>>();
// ...
// A state update function, takes an old state as an argument and must return the new state
neatState.update(
(AppState state) => state.copyWith(
// return the new state that is copy of an old state..
counter: state.counter + 1, // ..with incremented counter
),
);
Subscribe to the app state or some sub-state of the state (of course you can use map() on neatStream() to get an sub-state):
// Subscribe only to a counter substate of the whole app state
final StreamSubscription<int> _subscription = context
.neatSubStream(
(AppState state) => state.counter,
)
.listen(
(int counter) => print('counter=$counter'),
);