The spiral approach to software learning and development, which preserves a project history as a series of code snapshots or spirals, is used in this book.

The following three points are important in the spiral approach:

All three points are important to teach and learn these technologies.

Learning new software concepts and technologies is a challenging task. Learning in spirals, from simple to more advanced concepts but with concrete software applications, helps readers get a reasonable confidence level early on, and motivates them to learn by providing more useful applications. With each new spiral, the project grows and new concepts are introduced. A new spiral is explained with respect to the previous one. The difference between the two consecutive spirals is that the next spiral introduces the new code and modifies or deletes the old. This is called learning by anchoring to what we already understand. With a new spiral, we can go back to what we did previously and improve it. In this way, learning in spirals can touch the same topic several times, but each time, with more details in a better version.

Learning Dart, Second Edition, has 11 chapters. It begins with the basic elements of Dart and ends with a client/server application that uses MongoDB (http://www.mongodb.org/) for data persistence on the server-side.

Chapter 1, Dart – A Modern Web Programming Language, will help you understand what Dart is all about. Dart is presented as a major step forward in the web programming arena.

Chapter 2, Getting to Work with Dart, will help you get a firm grasp on how to program in Dart. The code and data structures in Dart and its functional principles are explained by exploring practical examples.

Chapter 3, Structuring Code with Classes and Libraries, will make you understand how to use Dart classes to organize code. Dart libraries will be introduced to show how complex software may be packaged.

Chapter 4, Modeling Web Applications with Model Concepts and Dartlero, will let you design graphically a small model in the Model Concepts tool, which is developed in Dart. A model is then represented in Dart as several classes that inherit some data and operations from the classes of the Dartlero model framework; this is also done in Dart.

Chapter 5, Handling DOM in a New Way, covers how to access HTML elements in Dart. Some elements will be even created in Dart and placed properly in the Document Object Model (DOM) of a web page. Dart will also handle user events, such as a click on a button. Finally, you will be able to create a simple game in Dart.

Chapter 6, Combining HTML5 Forms with Dart, will let you enter some data in a form. The data will be validated by HTML5 and Dart. Then, the valid data will be saved in the local storage of a browser.

Chapter 7, Building Games with HTML5 and Dart, will let you create a well-known memory game step by step, based on what you have learned already. Each step will be a new spiral represented as a complete project in Dart Editor. The first spiral will draw only a rectangle, while the last spiral will be a game that you may show to your friends.

Chapter 8, Developing Business Applications with Polymer Web Components, will help you create several web components using Polymer.dart. These web components will be used in the different sections of a single-page application. Three different projects with web components will be presented in this chapter.

Chapter 9, Modeling More Complex Applications with dartling, will let you discover how a graphical model can be transformed into a JSON document and then used to generate a complete model in Dart by using the dartling domain model framework together with its tools. The dartling follows the Model View Controller (MVC) pattern to separate a model from its views.

Chapter 10, Local Data and Client-Server Communication, will let you store application data in a local database called IndexedDB. The data will then be sent as a JSON document to a Dart server. Asynchronous programming with futures will be covered in this chapter.

Chapter 11, Data-Driven Web Applications with MySQL and MongoDB, will help you learn how to use database drivers to save (and load) data to (and from) a relational database and a NoSQL database. Data sent from a browser as a JSON document will be easily saved in MongoDB in the same JSON form. Two clients will exchange data with the server so that both of them will be up-to-date.

For this second edition, all the code and projects were updated to Dart version 1.11. Moreover, sections on the following topics were added:

In order to profit from this book, you need to have some basic experience in programming. It is also useful to have some understanding of HTML and CSS. What you really need to bring is your enthusiasm to learn how to become a web developer of the future. All the software used in the book is freely available on the Web:

One of the authors has already taught three times an introductory course to programming with some material from this book. Other educational resources for Dart can be found at http://ondart.me/.

The book is intended for (web) application programmers, game developers, and other software engineers. Because of its dual focus (Dart and HTML5), the book can appeal to web developers who want to learn a modern way of developing web applications and to developers who seek how to use HTML5. The audience includes mainstream programmers with an object-oriented background (Java, .NET, C++) as well as web programmers who use JavaScript to seek a more structured and tooled way of developing. Both groups will leverage their existing knowledge and expertise: the book will offer the first way of developing modern web applications using techniques they already know; it will give the second a more productive and engineered way of developing (business) web applications. The following article describes well what Dart has to offer for web developers of the future:

http://news.cnet.com/8301-1023_3-57613760-93/mixbook-sees-perfect-storm-for-googles-dart-language-q-a/

In this book, you will find a number of styles of text that distinguishe between different kinds of information. Here are some examples of these styles, and an explanation of their meaning.

Code words in text, database table names, folder names, filenames, file extensions, pathnames, dummy URLs, user input, and Twitter handles are shown as follows: "The last clause in the try statement should be on Exception catch(e) or, even better, a simple catch(e) to stop any type of error or exception."

A block of code is set as follows:

import 'dart:math';                                      (1)

void main() {
  var n = 0; // number of rabbits                        (2)

  print("The number of rabbits increases as:\n");        (3)
  for (int years = 0; years <= 10; years++) {            (4)
    n = (2 * pow(E, log(15) * years)).round().toInt();   (5)
    print("After $years years:\t $n animals");           (6)
  }
}

When we wish to draw your attention to a particular part of a code block, the relevant lines or items are set in bold:

try {
  int inp = int.parse(input);
} on FormatException {
  print ('ERROR: You must input an integer!');
}

Any command-line input or output is written as follows:

Observatory listening on http://127.0.0.1:49621

New terms and important words are shown in bold. Words that you see on the screen, in menus or dialog boxes for example, appear in the text like this: "Navigate to Tools | Preferences | Run and Debug, and change Break on Exceptions to None".

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