Cloning Internet Applications with Ruby

Table of Contents

Cloning Internet Applications with Ruby

Credits

About the Author

Acknowledgement

About the Reviewers

Preface

What this book covers

What you need for this book

Who this book is for

Conventions

Reader feedback

Customer support

Errata

Piracy

Questions

1. Cloning Internet Applications

Who would find this book useful

Popular Internet applications

Technologies used

Sinatra

Installing

Routes

Splitting a route into multiple files

Redirection

Filters

Static pages

Views

Layouts

Helpers

Error handling

DataMapper

Installing

Connecting to the database

Creating models

Defining associations between models

One-to-one

One-to-many

Many-to-many

Creating the database tables

Finding records

Haml

Installing

Using Haml

Haml and Ruby

How this book works

Caveat

Summary

2. URL Shorteners – Cloning TinyURL

All about URL shorteners

Main features

Designing the clone

Creating a short URL for each long URL

Automatically redirecting from a short URL to a long URL

Providing a customized short URL

Filtering undesirable words out

Previewing the long URL

Providing statistics

Technologies and platforms used

Sinatra

Haml

DataMapper

Blueprint CSS

Mashups

Google Chart API

HostIP

Heroku

Building the clone

Data model

Url

Link

Visit

Application flow

Deploying the clone

Summary

3. Microblogs – Cloning Twitter

All about microblogs

Twitter

Why Twitter?

Simple

A means to have public conversation

Fan versus friend

Understanding user behavior

Easy to share through text messaging

Easy to access through multiple devices and applications

Main features

Designing the clone

Posting statuses

Following users

Sending publicly directed messages

Sending privately directed messages

Re-tweeting

Public timeline

API

Authentication, access control, and user management

Third party authentication and access control

Authentication and user management

Scalability and stability

Technologies and platforms used

JSON

Mashups

RPX

Google ClientLogin

Gravatar

TinyURL

Heroku

Building the clone

Modeling the data

User

Status

Building the application flow

Authenticating and managing users

Displaying and updating statuses

Sending and displaying direct messages

Showing and forming relationships

Implementing the API

Deploying the clone

Deploying locally

Deploying to the cloud

Summary

4. Photo Sharing – Cloning Flickr

All about photo-sharing services

Flickr

Main features

Designing the clone

Authentication, access control, and user management

Albums and photos

Uploading and storing photos

Filesystem

Database

Comments

Annotations

Editing photos

Friendly URLs

Sharing photos

Technologies and platforms used

Mashups

RPX

Gravatar

Pixlr

Amazon Web Services Simple Storage Service (S3)

RightAWS

Building the clone

Configuration

Modeling the data

User

Album

Photo

Annotation

Comment

Building the application flow

Authenticating and managing users

Landing page

Managing albums

Uploading photos

Displaying photos

Annotating photos

Commenting on photos

Editing photos

Sharing photos

Deploying the clone

Deploying on a server

Summary

5. Social Networking Services – Cloning Facebook 1

All about social networking services

Facebook

Main features

User

Community

Content sharing

Designing the clone

Authentication, access control, and user management

Status updates

User activity feeds and news feeds

Friends list and inviting users to join

Posting to the wall

Sending messages

Attending events

Forming groups

Commenting on and liking content

Sharing photos

Blogging with pages

Technologies and platforms used

Mashups

Facebook Connect

Building the clone

Configuring the clone

Modeling the data

User

Request

Message

Album

Photo

Status

Group

Event

Page

Wall

Activity

Comment

Like

Summary

6. Social Networking Services – Cloning Facebook 2

Building the application flow

Structure of the application and flow

Authenticating and managing users

Landing page, news feed, and statuses

Inviting friends and friends list

Registering a Facebook application

Creating a cross-domain communication channel file

Writing the code

User page and activity feeds

Posting to a wall

Sharing photos

Managing albums

Uploading photos

Displaying photos

Annotating photos

Viewing friends' photos

Sending messages

Creating events

Forming groups

Sharing content through pages

Commenting and liking

Deploying the clone

Deploying locally

Deploying to the cloud

Summary

Index

Cloning Internet Applications with Ruby

Cloning Internet Applications with Ruby

Copyright © 2010 Packt Publishing

All rights reserved. No part of this book may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, without the prior written permission of the publisher, except in the case of brief quotations embedded in critical articles or reviews.

Every effort has been made in the preparation of this book to ensure the accuracy of the information presented. However, the information contained in this book is sold without warranty, either express or implied. Neither the author, nor Packt Publishing, and its dealers and distributors will be held liable for any damages caused or alleged to be caused directly or indirectly by this book.

Packt Publishing has endeavored to provide trademark information about all of the companies and products mentioned in this book by the appropriate use of capitals. However, Packt Publishing cannot guarantee the accuracy of this information.

First published: August 2010

Production Reference: 1110810

Published by Packt Publishing Ltd.

32 Lincoln Road

Olton

Birmingham, B27 6PA, UK.

ISBN 978-1-849511-06-3

www.packtpub.com

Cover Image by Asher Wishkerman (<[email protected]>)

Credits

Author

Chang Sau Sheong

Reviewer

Warren Brian Noronha

Francisco

Acquisition Editor

Douglas Paterson

Development Editor

Chaitanya Apte

Technical Editors

Alfred John

Kartikey Pandey

Indexer

Hemangini Bari

Editorial Team Leader

Aanchal Kumar

Project Team Leader

Lata Basantani

Project Coordinator

Jovita Pinto

Proofreader

Aaron Nash

Graphics

Geetanjali Sawant

Production Coordinator

Arvindkumar Gupta

Cover Work

Arvindkumar Gupta

About the Author

Chang Sau Sheong has more than 15 years experience in software application development and has spent much of his career working on Web and Internet-based applications. He started up elipva, an e-business software company, and was the Vice President of Product Engineering as well as Chief Architect. Subsequently he was Director of Software Development for Welcome Real-time, a bank loyalty software company, Engineering Director for Yahoo! Southeast Asia and Chief Technology Officer for Garena Online, an online game publishing company. He is currently the Director of the Applied Cloud Computing Lab in HP Labs Singapore, the research arm of Hewlett Packard, leading a team of engineers to implement cloud computing solutions.

Sau Sheong frequently writes for technical magazines and journals, including Java Report, Java World, and Dr. Dobb’s Journal. He is a passionate programmer who contributes to open source projects in various technologies including Ruby and Java. He has a wide range of experience in web application development on the Internet and mobile devices. His first book was ‘Ruby on Rails Mashup Projects’ in 2008, also published by Packt Publishing.

Sau Sheong hails from tropical Malaysia but spent most of his adult and working life in sunny Singapore, where he shares his spare time between enthusiastically writing software and equally enthusiastically playing Nintendo Wii with his wife and son. He has a Bachelors degree in Computer Engineering, a Masters degree in Commercial Law, and is a certified international arbitrator.

Acknowledgement

Firstly, many thanks to Douglas Paterson who agreed to this second book project, the book reviewers who have helped me improve my sprawling book and Jovita, the patient project coordinator who would wait patiently and gently prompt me as my chapter deadline approaches. I would also like to thank my Twitter and Hackerspace friends who on many occasions had to endure my relentless requests to test my ‘clones’ and provide feedback on them. A big thank you to Philippe Monnet who helped to review the first few chapters and even offered to re-draw a diagram for me. Final thanks to the love of my life, Wooi Ying, who suffered my erratic ‘nightlife’ in huddling in front of my laptop, creating software and writing yet another book (with her eyes rolling), and then there is Kai Wen who understands Daddy is finally an author.

About the Reviewers

Warren Noronha is an entrepreneur and a geek. Computers have been part of Warren’s life since he was four years old. He began his career as a system administrator, but ended up doing everything from security, design, to product development. He enjoys managing people as much as he does managing code or machines. Having worked with small startups as well as Fortune 500 companies, Warren is also a staunch supporter of free software and free speech. He has been a frequent speaker at various colleges and events, discussing subjects ranging from technology and media to launching a startup.

Warren loves working with new technologies, a trait which lead him to become one of the first users of GNU/Linux, Drupal, and Ruby on Rails, much before they grew exponentially and became mainstream technologies. He spends his time working on databases, distributed computing, and social computing, and enjoys using the Internet and communication technology to bridge the digital divide.

Francisco started out as a software architect and a project manager for various desktop and web applications. Then after falling out of love with outdated technologies and processes switched over to system admin and server infrastructure expert. Ruby was the catalyst to bring him back to the software development with agile processes. Currently a Mac lover and Ruby all in one backend expert. His experience in the server provisioning world and background as software developer resulted in quick rollout of fast, secure, and reliable backend Ruby on Rails applications for the enterprise.

Preface

We stand on the shoulders of giants. This has been true since the time of Newton (and even before) and it is certainly true now. Much of what we know and learn of programming, we learnt from the pioneering programmers before us and what we leave behind to future generations of programmers is our hard-earned experience and precious knowledge. This book is all about being the scaffolding upon which the next generation of programmers stands when they build the next Sistine Chapel of software.

There are many ways that we can build this scaffolding but one of the best ways is simply to copy from what works. Many programming books attempt to teach with code samples that the readers can reproduce and try it out themselves. This book goes beyond code samples. The reader doesn’t only copy snippets of code or build simple applications but have a chance to take a peek at how a few of the most popular Internet applications today can possibly be built. We explore how these applications are coded and also the rationale behind the way they are designed. The aim is to guide the programmer through the steps of building clones of the various popular Internet applications.

What this book covers

Chapter 1, Cloning Internet Applications gives a brief description of the purpose of the book, the target readers of the book, and a list of the four popular Internet applications we will be cloning in the subsequent chapters. The bulk of this chapter gives a brief run-down on the various technologies we will be using to build those clones.

Chapter 2, URL Shorteners – Cloning TinyURL explains about the first popular Internet application that we investigate and clone in the book, which is TinyURL. This chapter describes how to create a TinyURL clone, its basic principles, and algorithms used.

Chapter 3, Microblogs – Cloning Twitter. The clone in this chapter emulates one of the hottest and most popular Internet web applications now—Twitter. It describes the basic principles of a microblogging application and explains how to recreate a feature-complete Twitter clone.

Chapter 4, Photo -sharing – Cloning Flickr. Flickr is one of the most popular and enduring photo-sharing applications on the Internet. This chapter describes how the reader can re-create a feature complete photo-sharing application the simplest way possible, following the interface and style in Flickr.

Chapter 5, Social Networking Services – Cloning Facebook 1. The final two chapters describe the various aspects of Internet social networking services, focusing on one of the most popular out there now—Facebook. These two chapters also describe the minimal features of a social networking service and show the reader how to implement these features in a complete step-by-step guide. The first part is described in this chapter, which sets the groundwork for the clone and proceeds to describe the data model used in the clone.

Chapter 6, Social Networking Services – Cloning Facebook 2. The final chapter is part two in describing how to create a Facebook clone. This chapter follows on the previous chapter and describes the application flow of the Facebook clone we started earlier.

What you need for this book

Basic Ruby programming skills and basic level operational knowledge of Sinatra, DataMapper, Haml, Blueprint CSS, and MySQL.

Who this book is for

This book is written for web application programmers with an intermediate knowledge of Ruby. The reader should also know how web applications work and have used at least some of the cloned Internet services before.

A typical reader would be a programmer looking to write their own customized TinyURL, Twitter, Flickr, or Facebook. Programmers who want to include features of these Internet services into their own web applications will also find this book interesting.

Conventions

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

Code words in text are shown as follows: The many-to-many association can be defined with the has n and belongs_to methods.

A block of code is set as follows:

after :create, :create_wall

def create_wall

self.wall = Wall.create

self.save

end

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

$ sudo gem install Haml

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: The one big difference is of course, the list of statuses belongs to only that user, and there is a big follow button for the viewing user to follow him.

Note

Warnings or important notes appear in a box like this.

Tip

Tips and tricks appear like this.

Reader feedback

Feedback from our readers is always welcome. Let us know what you think about this book—what you liked or may have disliked. Reader feedback is important for us to develop titles that you really get the most out of.

To send us general feedback, simply send an e-mail to <[email protected]>, and mention the book title via the subject of your message.

If there is a book that you need and would like to see us publish, please send us a note in the SUGGEST A TITLE form on www.packtpub.com or e-mail .

If there is a topic that you have expertise in and you are interested in either writing or contributing to a book on, see our author guide on www.packtpub.com/authors.

Customer support

Now that you are the proud owner of a Packt book, we have a number of things to help you to get the most from your purchase.

Tip

Downloading the example code for this book

You can download the example code files for all Packt books you have purchased from your account at http://www.PacktPub.com. If you purchased this book elsewhere, you can visit http://www.PacktPub.com/support and register to have the files e-mailed directly to you.

Errata

Although we have taken every care to ensure the accuracy of our content, mistakes do happen. If you find a mistake in one of our books—maybe a mistake in the text or the code—we would be grateful if you would report this to us. By doing so, you can save other readers from frustration and help us improve subsequent versions of this book. If you find any errata, please report them by visiting http://www.packtpub.com/support, selecting your book, clicking on the errata submission form link, and entering the details of your errata. Once your errata are verified, your submission will be accepted and the errata will be uploaded on our website, or added to any list of existing errata, under the Errata section of that title. Any existing errata can be viewed by selecting your title from http://www.packtpub.com/support.

Piracy

Piracy of copyright material on the Internet is an ongoing problem across all media. At Packt, we take the protection of our copyright and licenses very seriously. If you come across any illegal copies of our works, in any form, on the Internet, please provide us with the location address or website name immediately so that we can pursue a remedy.

Please contact us at <[email protected]> with a link to the suspected pirated material.

We appreciate your help in protecting our authors, and our ability to bring you valuable content.

Questions

You can contact us at <[email protected]> if you are having a problem with any aspect of the book, and we will do our best to address it.

Chapter 1. Cloning Internet Applications

This book is about copying. Copying has an unpleasant reputation in these copyright and intellectual property sensitive times, but it's probably unknown to many, that it has an illustrious past. When we were babies, the main way we learnt was through copying what our parents did. If you have young children you soon learn to your regret the first time you utter any insalubrious words and how quickly your child copies your exclamation and mannerisms. Our number system was copied from the Arabs (that's why they are called Arabic numerals) but it was first used by the Indians from the Indian subcontinent, and subsequently copied by the Arabs in the Middle-East. The English language regularly copies words from other languages. In fact the word 'copy' comes from the Old French word copie which comes from the Medieval Latin word copia.

That is not to say infringing copyright is the right thing to do when someone else has spent tremendous effort in coming up with the original. However, it should be recognized that not all things are copyrightable, patentable, or can be trademarked, and that is for a good reason. Ideas for example are generally not considered as intellectual property. Copyright is the protection of expressions of ideas, not the protection of the ideas themselves. Patent law is used for the protection of inventions for a limited time in return for the disclosure of the invention. Again it is not a protection of ideas; the concept of patent law is to promote the liberation of the idea in exchange for limited monopoly. Google is well known to have dominance in the search engine market but it doesn't mean it has monopoly on search engines. Anyone else is free to write his/her own search engine (though taking part of Google's search engine code to write your own search engine is copyright infringement).

This idea of copying is the basis of the book you are holding. In short, the premise of this book is to learn how each of the popular Internet applications we clone work through copying the ideas behind them.

In this chapter we will cover:

A brief description of the type of people who would like to read this book

The popular Internet applications described in this book and why we chose them

The various technologies used in this book, including Sinatra, DataMapper, and Haml

Who would find this book useful

The primary audience for this book are Ruby programmers with an intermediate level of experience in Ruby as well as web application programming. This sounds quite limiting but in reality if you have any intermediate level of programming in any object-oriented language you should be able to follow the implementations with relative ease. Of course, if you know something about the Ruby programming language it helps a lot too.

The technology stack that we will be using for these clones is slightly off the usual track for the Ruby on Rails crowd. The main reason is because it's a simpler stack to use. Ruby on Rails, while extremely easy to use and very powerful, has a lot of added frills to the framework, which adds on unnecessary complexity for a book that focuses on clones and features of the clones only. The chosen stack however does not different too greatly for programmers who are familiar with Rails. In this chapter we will go through all that is needed to follow the rest of the chapters in this book.

So why are we interested in cloning these applications at all, since we can't possibly build a clone that is better than the original? There are plenty of reasons for doing so but let me just give four common ones:

To learn how these applications work. We use them all the time and while we would know how these applications functionally work, cloning them will teach us how these features can be implemented. Although the implementation is not definitive, at least learning how difficult or easy it is to clone them gives us a better appreciation of how things work behind the scenes to provide us with the features.

To incorporate features of the clones into your own application. As you will see in this book, each chapter shows how key features in those applications are implemented. If you want to build these key features into your own application, learning how these features are implemented will give you an insight into building them for your own use.

To build a customized clone. While each popular Internet application has plenty of features to go with, there will be special niche needs that can only be fulfilled by a customized version of that application.

Learning the technology stack. The best way to learn any new technology stack is to build something with it. Going through the chapters in this book will give you ample exercise in this stack.

If you find yourself having any of the above needs then this book is for you.

Popular Internet applications

Why did we choose the Internet applications in this book and not others? Firstly and most obviously, the applications must be popular and have a large number of users. Secondly the application should be a mainstream one for consumers and not for businesses. We want applications that have a more direct interface to the final consumers of the application. Thirdly, we don't want to deal with payment related issues in this book so any e-commerce applications are left alone. The reason is simple—e-commerce is no longer rocket science but implementing payment well is still not a trivial undertaking, and we did not want to mislead users into believing it is easy to clone payment features. Finally (and most importantly for me) the applications we chose to clone must also be easy to implement and would fit in nicely into a single chapter.

With these criteria, we have picked the following small number of applications to cover in this book:

A URL shortener—TinyURL

A microblogging application—Twitter

A photo sharing application—Flickr

A social networking service—Facebook

It's interesting that none of the crop of popular Internet applications we are cloning in this book is the true original implementation of the main idea in that application. There have been URL shorteners before TinyURL, there were micro-blogging sites before Twitter, photo-sharing before Flickr, and definitely social networking services before Facebook. However, each of these is, as of writing, the most popular service of its kind.

Technologies used

The technology stack used in this book consists of mainly Ruby-only libraries and tools:

Sinatra—a Ruby domain-specific language (DSL) with a minimalist approach in building web applications

DataMapper—a Ruby object-relational mapping library

Haml—a Ruby-friendly markup language that allows us to manipulate XHTML of any web document programmatically

We will be going in depth in each of these technologies. While this seems a bit too much to cover within a single chapter, each technology is essentially not complex. Once you have grasped the basics of each technology, a quick reference back to the documentation will allow you do to anything you want.

Sinatra

Sinatra is a domain-specific language built with Ruby, used to build web applications. Sinatra was created with a minimalist approach in mind and focuses on the fastest way to get a web application up and running. For example, you can create a simple web application with just the following in a file named hello.rb:

require 'rubygems'

require 'sinatra'

get '/' do 

Hello world, it's #{Time.now} at the server!

end

After that just run the following command:

ruby hello.rb

Then go to http://localhost:4567/ and you will see the hello statement with the current time. Writing a web application becomes almost trivial up to this stage. Of course as web applications become more complex, unlike other full-fledged web frameworks such as Ruby on Rails or Merbs, you will need to write more code.

As mentioned earlier, one of the reasons why we chose Sinatra is because of its simplicity and minimalist approach. In a book that teaches how application features can be implemented, more complex frameworks can often add to the clutter because of 'the way it works' rather than clarifying the implementation of the feature. As a result, a DSL such as Sinatra, where nothing is taken for granted, is very useful as a teaching tool.

Installing

Sinatra can be easily installed through Rubygems:

$ sudo gem install sinatra

That's all there is to it. You will be able to use Sinatra immediately after that.

Routes

In Sinatra, a route is HTTP method and a URL matching pattern. For example, this is a route:

get '/' do

  ...