Corresponding code for my YouTube tutorial series for learning the BLoC pattern

friend_list.dart

import 'dart:async';

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.red,
      ),
      home: FriendList(),
    );
  }
}

class FriendList extends StatefulWidget {
  @override
  _FriendListState createState() => _FriendListState();
}

class _FriendListState extends State<FriendList> {
  List<String> _friends = [];
  final _friendsController = StreamController<List<String>>();

  final _textController = TextEditingController();

  @override
  void dispose() {
    _friendsController.close();
    _textController.dispose();
    super.dispose();
  }

  void addFriend(String value) {
    _friends.add(value);
    _friendsController.sink.add(_friends);
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text("Friend List"),
      ),
      body: Column(
        children: <Widget>[
          Expanded(
            child: _buildFriendList(),
          ),
          Padding(
            padding: EdgeInsets.all(8.0),
            child: TextField(
              controller: _textController,
              decoration: InputDecoration(
                border: OutlineInputBorder(),
                hintText: 'Enter New Friend',
              ),
              onSubmitted: (value) {
                addFriend(value);
                _textController.clear();
              },
            ),
          ),
        ],
      ),
    );
  }

  Widget _buildFriendList() {
    return StreamBuilder<List<String>>(
        stream: _friendsController.stream,
        builder: (context, snapshot) {
          if (snapshot.hasData) {
            return ListView.separated(
              itemCount: _friends.length,
              separatorBuilder: (context, index) => Divider(),
              itemBuilder: (context, index) {
                return ListTile(
                  title: Text('${snapshot.data[index]}'),
                );
              },
            );
          }
          return Column(
            mainAxisAlignment: MainAxisAlignment.center,
            children: <Widget>[
              Icon(Icons.add),
              Text('Add New Friend'),
            ],
          );
        });
  }
}

streams.dart

import 'dart:async';
import 'dart:convert';
import 'dart:io';

void main() {
  //streamFromIterable();
  //streamUsingController();
  // readNameFile();
}

void streamFromIterable() {
final list = [2, 3, 8, 9, 12];
final stream = Stream.fromIterable(list);
final subscription = stream.where((value) => value.isEven).listen(null);

  subscription.onData((value) => print(value));
Another way
subscription.onData((value){
  if(value == 9){
    subscription.cancel();
  }
  print(value);
});
  subscription.onError((err) => print('Error $err'));
  subscription.onDone(() => print('Done'));
}

void streamUsingController() {
  final _controller = StreamController<int>.broadcast();
  Stream<int> counterStream = _controller.stream;

  final sub1 = counterStream.listen((value) => print(value));
  final sub2 = counterStream.listen((value) => print(value));

  _controller.sink.add(1);
  Future.delayed(Duration(milliseconds: 2000), () {
    _controller.sink.add(2);
    _controller.close();
  });
    //_controller.close();
}

void readNameFile() {
  final file = File('names.txt');
  file.openRead()
    .transform(utf8.decoder)
    .transform(customTransformer)
    .transform(LineSplitter())
    .listen((value){
      print("Received");
      print(value);
    });
}

var customTransformer = StreamTransformer<String, String>.fromHandlers(
  handleData: (value, sink) {
      sink.add(value.toUpperCase());
  }
);