Dart tip of the day / Lecture 20 / Stream

stream_tutorial.dart

import 'dart:async';
import 'dart:math';

import 'package:flutter/material.dart';

void main() async {
  // var firstUser = await getUserName();
  // var secondUser = await getUserName();
  // var thirdUser = await getUserName();

  print('헬로우 월드');
  // await for (var user in getUserNameStream()) {
  //   print('user : $user');
  // }
  // print('헬로우 월드 2');

  var userNameStream =
      getUserNameStream()
          .asyncMap((username) {
            return '$username is awesome!';
          })
          .distinct()
          .asBroadcastStream();

  StreamSubscription<String>? subscription;

  subscription = userNameStream.listen(
    (user) {
      print('user : $user');

      if (user == 'Bob') {
        subscription?.cancel();
      }
    },
    onDone: () {
      print('onDone');
    },
  );

  // userNameStream.listen(
  //   (user) {
  //     print('user : $user');
  //
  //     if (user == 'Bob') {
  //       subscription?.cancel();
  //     }
  //   },
  //   onDone: () {
  //     print('onDone');
  //   },
  // );
}

Stream<String> getUserNameStream() async* {
  List<String> names = ["John", "Jane", "Bob", "Alice", "Tom"];
  await Future.delayed(const Duration(seconds: 1));
  yield "Bob";
  await Future.delayed(const Duration(seconds: 3));
  yield "Bob";
  await Future.delayed(const Duration(seconds: 2));
  yield names[Random().nextInt(names.length)];
}

Future<String> getUserName() async {
  List<String> names = ["John", "Jane", "Bob", "Alice", "Tom"];
  await Future.delayed(const Duration(seconds: 1));
  return names[Random().nextInt(names.length)];
}