Discussion on "Dash Tips: Using Freezed with StateNotifier"

Ryan Edge · 2020-04-10T02:42:24.748Z

Justification Previously I wrote about using freezed with the awesome bloc library. Now let's look at the same example implemented with state_notifier to get a good understanding of the differences. The Counter State Notifier import 'package:freezed...

How to add something like loading state?

I tried:

@freezed
abstract class CounterState with _$CounterState {
  const factory CounterState.initial([@Default(0) int value]) = _Initial;
  const factory CounterState.loading() = _Loading;
  const factory CounterState.current(int value) = _Current;
}

Of course I get an error if I try to use it in notifier, because current looses it:

The getter 'value' isn't defined for the type 'CounterState'.

How to go about it?

Thanks

What I did (to present loading state example) is:

@freezed
abstract class CounterState with _$CounterState {
  const factory CounterState.initial([@Default(0) int value]) = _Initial;
  const factory CounterState.loading(int value) = _Loading;
  const factory CounterState.current(int value) = _Current;
}

class CounterStateNotifier extends StateNotifier<CounterState>
    with LocatorMixin {
  CounterStateNotifier() : super(CounterState.initial());

  void increment() {
    state = CounterState.loading(state.value);
    Timer(
      Duration(seconds: 1),
      () => state = CounterState.current(state.value + 1),
    );
  }
}

StateNotifierBuilder(
              stateNotifier: context.watch<CounterStateNotifier>(),
              builder: (context, CounterState state, _) => state.when(
                initial: (value) => Text(
                  '$value',
                  style: Theme.of(context).textTheme.headline4,
                ),
                loading: (_) => CircularProgressIndicator(),
                current: (value) => Text(
                  '$value',
                  style: Theme.of(context).textTheme.headline4,
                ),
              ),
            )

But that is obviously 'hack'. Any tip? Remi Rousselet / Ryan Edge

Features like middlewares are still doable here though:

The setter of "state" is overridable.

Most definitely! StateNotifier can be scaled up to match Bloc capabilities. That point is more to highlight reasons Bloc may be overkill.

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Dash Tips: Using Freezed with StateNotifier

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