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Table Of Contents

Dart By Example

By : David Mitchell

3 (2)

Dart By Example

3 (2)

By: David Mitchell

Overview of this book

Designed to create next generation apps, Google’s Dart offers a much more robust framework and also supersedes JavaScript in several aspects. Familiar yet innovative, compact yet scalable, it blows away the accumulated JavaScript legacy limitations. Dart was designed for great tool-ability and developer productivity, allowing you to create better application faster than before. Google chose it for their billion dollar advertising business and you have its power for your projects too. This book will introduce you the Dart language starting from its conception to its current form, and where it headed is through engaging substantial practical projects. You will be taken through building typical applications and exploring the exciting new technologies of HTML5. With example code projects such as a live data monitoring and viewing system, a blogging system, a slides presentation application, and more, then this book will walk you through step by step through building data-driven web applications with ease and speed.

Preface

Preface

What this book covers

What you need for this book

Who this book is for

Conventions

Reader feedback

Customer support

Free Chapter

1. Starting the Text Editor

1. Starting the Text Editor

Defining Dart

History of Web scripting

The origins of Dart

Downloading the tools

Building your first application

Debugging a Dart application

Summary

2. Advancing the Editor

2. Advancing the Editor

The next steps for the text editor

Building the dialog package

The command-line app for source code statistics

Building web interfaces with Dart

Compiling to JavaScript

Summary

3. Slideshow Presentations

3. Slideshow Presentations

Building a presentation application

Accessing private fields

Mixin' it up

Changing the colors

Adding a date

Timing the presentation

An overview of slides

Handout notes

Summary

4. Language, Motion, and Sound

4. Language, Motion, and Sound

Going fullscreen

Adding metadata

Exploring the intl package

Working with dates

Animating slides

Playing sound in the browser

Summary

5. A Blog Server

5. A Blog Server

The Hello World server example

A blog server

Introducing Dart's server frameworks

Deployment

Load testing

Summary

6. Blog Server Advanced

6. Blog Server Advanced

Logging

A blog editor

Caching

Watching the filesystem

XML feed generation

The JSON feed generation

Static generation

Introducing the await and async keywords

Load testing revisited

Summary

7. Live Data Collection

7. Live Data Collection

Kicking off the earthquake monitoring system

Introducing the data source

Exploring the GeoJSON format

Logging

Saving to the database

Introducing the pgAdmin GUI

Observing the Dart VM internals

Unit testing

Summary

8. Live Data and a Web Service

8. Live Data and a Web Service

Freeing the data

Creating the web service

Recapping the system so far

Consuming application

Summary

9. A Real-Time Visualization

9. A Real-Time Visualization

Iteration overview

Application overview

Notifying the user of an update

Plotting the user's location

Sorting the feature list

Documenting Dart code with dartdoc

Summary

10. Reports and an API

10. Reports and an API

Recapping the earthquake system

Advancing the REST API

Passing parameters to the API

Posting on the API

Summary

Index

Index

Introducing the await and async keywords

The await and async keywords were introduced in Dart 1.9.4 in order to simplify asynchronous operations. Consider the following call to a method that returns Future:

obj.method().then(handlerFunction)

This is fine for the post part, but what if things get more complicated and handlerFunction returns a future too?

obj.method().then(handlerFunction).then(handlerFunction2);

Things are starting to get complicated already—debugging is not straightforward. Ideally, we would want to deal with one part of the chain at a time and hold up the execution of statements until a desired operation is complete. This is what await allows:

var f1 = await obj.aMethod();
var result = await f1.aMethod();

Functions and methods to be called with await return Future. They must also be declared as async in the method's header, as does the function using the await call:

class Foo{
   Future<int> aMethod() async {
   return await aFunction();
  }
}

The async and await keywords...

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