futures examples

main.dart

// Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

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

Future<void> printDailyNewsDigest() async {
  var newsDigest = await gatherNewsReports();
  print(newsDigest);
}

main() {
  print('Start of app');
  printSomething();
  printDailyNewsDigest();
  printWinningLotteryNumbers();
  printWeatherForecast();
  printBaseballScore();
}

printSomething() {
  print('continue with other news');
  // This blocks without await
//   var list= await List<int>.generate(10000000, (int index) => index * index);
//   print('list ${list[10]}');
  
  var future=() async {
    return  await List<int>.generate(1000000, (int index) => index * index);
  };
  
  future().then((l){
    print(l[10]);
    print('Got the news');
  });
  
//   Future.delayed(Duration(seconds: 10), () => print("5678"));
//   print('end');
}

printWinningLotteryNumbers() {
  print('Winning lotto numbers: [23, 63, 87, 26, 2]');
}

printWeatherForecast() {
  print("Tomorrow's forecast: 70F, sunny.");
}

printBaseballScore() {
  print('Baseball score: Red Sox 10, Yankees 0');
}

const news = '<gathered news goes here>';
const oneSecond = Duration(seconds: 1);

// Imagine that this function is more complex and slow. :)
Future<String> gatherNewsReports() =>
    Future.delayed(oneSecond, () => news);

// Alternatively, you can get news from a server using features
// from either dart:io or dart:html. For example:
//
// import 'dart:html';
//
// Future<String> gatherNewsReportsFromServer() => HttpRequest.getString(
//      'https://www.dartlang.org/f/dailyNewsDigest.txt',
//    );