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  • Flutter BLoC, RxDart combineLatestStream BehaviorSubject On Submit
    lang/dart 2020. 9. 18. 08:30

    Flutter BLoC, RxDart combineLatestStream BehaviorSubject

    pubspec.yaml

    dependencies:
      flutter:
        sdk: flutter
    
    
      # The following adds the Cupertino Icons font to your application.
      # Use with the CupertinoIcons class for iOS style icons.
      cupertino_icons: ^0.1.3
    
      rxdart: ^0.24.1
      #rxdar: ^0.16.7

    main.dart

    import 'package:flutter/material.dart';
    import 'src/app.dart';
    
    void main() => runApp(App());

    src/app.dart

    import 'package:flutter/material.dart';
    import 'screens/login_screen.dart';
    import 'blocs/provider.dart';
    
    class App extends StatelessWidget {
      @override
      Widget build(BuildContext context) {
        return Provider(
          child: MaterialApp(
            title: 'Login',
            home: Scaffold(
              appBar: AppBar(
                title: Text('LoginForm'),
              ),
              body: LoginScreen(),
            ),
          ),
        );
      }
    }

    src/screens/login_screen.dart

    import 'package:flutter/material.dart';
    import '../blocs/bloc.dart';
    import '../blocs/provider.dart';
    
    class LoginScreen extends StatefulWidget {
      @override
      _LoginScreenState createState() => _LoginScreenState();
    }
    
    class _LoginScreenState extends State<LoginScreen> {
    
      @override
      Widget build(BuildContext context) {
        final bloc = Provider.of(context);
    
        return Container(
          margin: EdgeInsets.all(8.0),
          child: Form(child: 
            Column(children: <Widget>[
              fieldEmail(bloc),
              fieldPassword(bloc),
              _submit(bloc),
              ],
            ),
          ),
        );
      }
    
      Widget fieldEmail(Bloc bloc) {
        return StreamBuilder(
          stream: bloc.email,
          builder: (context, snapshot) {
            return TextField(
              onChanged: bloc.changeEmail,
              keyboardType: TextInputType.emailAddress,
              decoration: InputDecoration(
                labelText: 'Email',
                hintText: 'useanem@domain.com',
                errorText: snapshot.error,
              ),
            );
          }
        );
      }
    
      Widget fieldPassword(Bloc bloc) {
        return StreamBuilder(
          stream: bloc.password,
          builder: (context, snapshot) {
            return TextField(
              onChanged: bloc.changePassword,
              obscureText: true,
              decoration: InputDecoration(
                labelText: 'Password',
                hintText: 'over 3 charactor',
                errorText: snapshot.error,
              ),
            );
          }
        );
      }
    
      Widget _submit(Bloc bloc) {
        return StreamBuilder(
          stream: bloc.submitValid,
          builder: (context, snapshot) {
            return RaisedButton(
              color: Colors.blue,
              child: Text('Submit', style: TextStyle(color: Colors.white),),
              onPressed: snapshot.hasError ? null : bloc.submit,
            );
          }
        );
      }
    }

    src/blocs/bloc.dart

    import 'dart:async';
    import 'package:flutter/foundation.dart';
    
    import 'validators.dart';
    import 'package:rxdart/rxdart.dart';
    
    class Bloc extends Object with Validators {
      // https://pub.dev/documentation/rxdart/latest/rx/BehaviorSubject-class.html
      final _email = BehaviorSubject<String>();
      final _passwd = BehaviorSubject<String>();
    
      Stream<String> get email => _email.stream.transform(validatorEmail);
      Stream<String> get password => _passwd.stream.transform(validatorPassword);
      // https://pub.dev/documentation/rxdart/latest/rx/CombineLatestStream-class.html
      // https://pub.dev/documentation/rxdart/latest/rx/CombineLatestStream/combine2.html
      // Stream<bool> get submitValid => Observable.combineLatest2(email, password, (e, p)=>e&&p);
      Stream<bool> get submitValid => CombineLatestStream([email, password], (_)=>true);
    
      Function(String) get changeEmail => _email.sink.add;
      Function(String) get changePassword => _passwd.sink.add;
    
      submit() {
        final validEmail = _email.value;
        final validPassword = _passwd.value;
    
        print('Email is $validEmail');
        print('Password is $validPassword');
      }
    
      dispose() {
        _email.close();
        _passwd.close();
      }
    }

    src/blocs/provider.dart

    import 'package:flutter/material.dart';
    import 'bloc.dart';
    
    class Provider extends InheritedWidget {
      final bloc = Bloc();
    
      Provider({key, Widget child}) : super(key: key, child: child);
    
      // @override
      // bool updateShuldNotify(_) => true;
      @override
      bool updateShouldNotify(InheritedWidget oldWidget) => true;
      /*{
        throw UnimplementedError();
      }*/
    
      static Bloc of(BuildContext context) {
        // ignore: deprecated_member_use
        // return (context.inheritFromWidgetOfExactType(Provider) as Provider).bloc;
        // https://stackoverflow.com/a/59304297
        return (context.dependOnInheritedWidgetOfExactType<Provider>()).bloc;
    
      }
    }

    src/blocs/validators.dart

    import 'dart:async';
    
    class Validators {
      final validatorEmail = StreamTransformer<String, String>.fromHandlers(
        handleData: (String email, sink) {
          if( email.contains('@') ){
            sink.add(email);
          } else {
            sink.addError('Enter a valid email');
          }
        }
      );
    
      final validatorPassword = StreamTransformer<String, String>.fromHandlers(
        handleData: (String passwd, sink) {
          if( passwd.length >= 3 ) {
            sink.add(passwd);
          } else {
            sink.addError('password must be at leat 3 characters');
          }
        }
      );
    }

    Flutter State

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