AsyncAction bug

[yohom]

Dispatch an AsyncAction invokes the middleware's beforeAction method twice.I tweak a little on your example:

import 'dart:async';

import 'package:flutter/material.dart' hide State;
import 'package:flutter_redurx/flutter_redurx.dart';

class State {
  State({this.title, this.count});
  final String title;
  final int count;
}

/***************** tweaked ****************/
class Increment extends AsyncAction<State> {
  @override
  Future<Computation<State>> reduce(State state) async {
    print('in action: Increment: $state');
    return (State state) => State(title: state.title, count: state.count + 1);
  }
}
/***************** tweaked ****************/

void main() {
  /***************** tweaked ****************/
  final store =
      Store<State>(State(title: 'Flutter-ReduRx Demo Title', count: 0))
          .add(LogMiddleware());
  /***************** tweaked ****************/
  runApp(Provider(store: store, child: MyApp()));
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter-ReduRx Demo',
      theme: ThemeData(primarySwatch: Colors.pink),
      home: MyHomePage(),
    );
  }
}

class MyHomePage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Connect<State, String>(
          convert: (state) => state.title,
          where: (prev, next) => next != prev,
          builder: (title) {
            print('Building title: $title');
            return Text(title);
          },
        ),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            Text('You have pushed the button this many times:'),
            Connect<State, String>(
              convert: (state) => state.count.toString(),
              where: (prev, next) => next != prev,
              builder: (count) {
                print('Building counter: $count');
                return Text(count, style: Theme.of(context).textTheme.display1);
              },
            ),
          ],
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: () => Provider.dispatch<State>(context, Increment()),
        tooltip: 'Increment',
        child: Icon(Icons.add),
      ),
    );
  }
}

This will output

12:40:44.015 1 info flutter.tools flutter: Before action: Increment: Instance of 'State'
12:40:44.015 2 info flutter.tools flutter: in action: Increment: Instance of 'State'
12:40:44.015 3 info flutter.tools flutter: Before action: Increment: Instance of 'State'
12:40:44.015 4 info flutter.tools flutter: After action: Increment: Instance of 'State'
12:40:44.038 5 info flutter.tools flutter: Building counter: 1

[leocavalcante]

I'm adding a [wontfix] for now because this isn't a bug, it is a expected behavior. Before middlewares are indeed computed twice at redurx.dart#L47 and redurx.dart#L50. That is because being a asynchronous execution, the first call is right after the Action dispatch e the second call is when Action fulfilled its asynchronous behavior, but didn't added it's computation as a new state to the Store.

But sure, I would like to discuss if this is a good behavior. What do you think? Are you having trouble with it?

[leocavalcante]

Closed due inactivity.