Flutter redux error snackbar

error_snackbar.dart

import 'package:flutter/foundation.dart';
import 'package:flutter/material.dart';
import 'package:flutter/widgets.dart';
import 'package:flutter_redux/flutter_redux.dart';
import 'package:pjapp_flutter/actions/errors_action.dart';
import 'package:pjapp_flutter/models/app_state.dart';
import 'package:redux/redux.dart';

class ErrorSnackbar extends StatelessWidget {
  ErrorSnackbar({Key key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return StoreConnector<AppState, _ViewModel>(
      onWillChange: (_viewModel) {
        final snackBar = SnackBar(
          content: Text(_viewModel.errormsg),
          backgroundColor: Colors.red,
          action: SnackBarAction(
            label: 'Dismiss',
            onPressed: () {
              Scaffold.of(context).hideCurrentSnackBar(reason: SnackBarClosedReason.dismiss);
            },
          ),
        );
        Scaffold.of(context).showSnackBar(snackBar);
        _viewModel.errorHandledCallback();
      },
      converter: _ViewModel.fromStore,
      distinct: true,
      builder: (context, vm) {
        // TODO: Don't use a UI Widget here. This "Widget" should not be visible because its only there to display the snackbar if needed
        return const Text("");
      },
    );
  }
}

class _ViewModel {
  final String errormsg;
  final Function errorHandledCallback;

  _ViewModel({
    @required this.errormsg,
    @required this.errorHandledCallback,
  });

  static _ViewModel fromStore(Store<AppState> store) {
    return _ViewModel(
        errormsg: store.state.error,
        errorHandledCallback: () {
          store.dispatch(new ClearError());
        }
    );
  }

  @override
  bool operator ==(Object other) =>
      identical(this, other) ||
          other is _ViewModel &&
              runtimeType == other.runtimeType &&
              errormsg == other.errormsg;

  @override
  int get hashCode => errormsg.hashCode;

}