نحوه استفاده از RxDart به همراه الگوی بلاک در فلاتر

PublishSubject<int> subject = new PublishSubject<int>();

/*this listener below will print every integer added to the subject: 1, 2, 3, ...*/
subject.stream.listen(print);
subject.add(1);
subject.add(2);

/*but this listener below will print only the integer added after his initialization: 3, .../*
subject.stream.listen(print);
subject.add(3);

BehaviorSubject<int> subject = new BehaviorSubject<int>();
subject.stream.listen(print); // prints 1,2,3 
subject.add(1);
subject.add(2);
subject.add(3);

subject.stream.listen(print); // prints 3

ReplaySubject<int> subject = new ReplaySubject<int>();

subject.add(1);
subject.add(2);
subject.add(3);

subject.stream.listen(print); // prints 1, 2, 3

import 'package:flutter/material.dart';

void main() => runApp(new MyApp());

class MyApp extends StatelessWidget {

  @override
  Widget build(BuildContext context) {
    return new MaterialApp(
      title: 'Flutter Demo',
      theme: new ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: new MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);

  final String title;

  @override
  _MyHomePageState createState() => new _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  int _counter = 0;

  void _incrementCounter() {
    setState(() {
      _counter++;
    });
  }

  void _decrementCounter() {
    setState(() {
      _counter--;
    });
  }

  @override
  Widget build(BuildContext context) {
    return new Scaffold(
      appBar: new AppBar(
      ),
      body: new Center(
        child: new Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            new Text('You have pushed the button this many times:',),
            new Text('$_counter', style: Theme.of(context).textTheme.display1),
          ],
        ),
      ),
      floatingActionButton: new Column(mainAxisAlignment: MainAxisAlignment.end, children: <Widget>[
        new Padding(padding: EdgeInsets.only(bottom: 10), child:
          new FloatingActionButton(
            onPressed: _incrementCounter,
            tooltip: 'Increment',
            child: new Icon(Icons.add),
          )
        ),
        new FloatingActionButton(
          onPressed: _decrementCounter,
          tooltip: 'Decrement',
          child: new Icon(Icons.remove),
        ),
      ])
    );
  }
}

import 'package:rxdart/rxdart.dart';

class CounterBloc {

  int initialCount = 0; //if the data is not passed by paramether it initializes with 0
  BehaviorSubject<int> _subjectCounter;

  CounterBloc({this.initialCount}){
   _subjectCounter = new BehaviorSubject<int>.seeded(this.initialCount); //initializes the subject with element already
  }

  Observable<int> get counterObservable => _subjectCounter.stream; 

  void increment(){
    initialCount++;
    _subjectCounter.sink.add(initialCount);
  }

  void decrement(){
    initialCount--;
    _subjectCounter.sink.add(initialCount);
  }

  void dispose(){
    _subjectCounter.close();
  }
  
}

import 'package:flutter/material.dart';
import 'package:bloc_example/bloc/CounterBloc.dart';

void main() => runApp(new MyApp());

class MyApp extends StatelessWidget {

  @override
  Widget build(BuildContext context) {
    return new MaterialApp(
      title: 'Flutter Demo',
      theme: new ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: new MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);

  final String title;

  @override
  _MyHomePageState createState() => new _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {

  CounterBloc _counterBloc = new CounterBloc(initialCount: 0);

  @override
  Widget build(BuildContext context) {
    return new Scaffold(
      appBar: new AppBar(
      ),
      body: new Center(
        child: new Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            new Text('You have pushed the button this many times:'),
            new StreamBuilder(stream: _counterBloc.counterObservable, builder: (context, AsyncSnapshot<int> snapshot){
              return new Text('${snapshot.data}', style: Theme.of(context).textTheme.display1);
            })
          ],
        ),
      ),
      floatingActionButton: new Column(mainAxisAlignment: MainAxisAlignment.end, children: <Widget>[
        new Padding(padding: EdgeInsets.only(bottom: 10), child:
          new FloatingActionButton(
            onPressed: _counterBloc.increment,
            tooltip: 'Increment',
            child: new Icon(Icons.add),
          )
        ),
        new FloatingActionButton(
          onPressed: _counterBloc.decrement,
          tooltip: 'Decrement',
          child: new Icon(Icons.remove),
        ),
      ])
    );
  }

  @override
  void dispose() {
    _counterBloc.dispose();
    super.dispose();
  }
  
}