Cesare Rocchi - iCloud for Developers: Automatically Sync Your iOS Data, Everywhere, All the Time

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When a book shows just one author name on the cover, we tend to think its the result of a single-person effort. Thats far from the truth. Without the help of the many people who surrounded me (though just virtually) during the writing, this book would not have seen the light. I am happy to thank Andy and Dave for the opportunity to publish this book. John Osborn, the editor, deserves a special mention because he helped me throughout all the phases of the writing, from organizing the content to tweaking obscure sentences. Finally, Id like to thank all the awesome technical reviewers who provided feedback on all the chapters and the code attached to this book.

• Jeff Holland

• Matt Galloway ( http://www.galloway.me.uk )

• Felipe Laso Marsetti ( http://ife.li/ )

• Marcio Valenzuela ( http://www.santiapps.com )

• Bear Cahill ( http://www.brainwashinc.com )

• Tony Dahbura ( http://www.fullmoonmanor.net/FullMoonManor/Welcome.html )

• Jonathan Penn ( http://cocoamanifest.net )

You are an iOS developer with a successful application to your credit, but your customers want more and pepper you with questions: How do I back up my data? How can I replicate on my iPad the data that Ive created on my iPhone? If I buy a new iPhone, will I lose the data in my apps when I switch devices?

Youd like to support your users, but you dont have the skills or time to build a back-end system that could provide the safe and reliable backups your customers say they want. Moreover, the thought of synchronizing data across multiple devices gives you a headache.

If any of this applies to you, iCloud is a good candidate for solving your problems and giving your users the features theyve requested. This book will teach you how to work with iCloud, hook up with its APIs, work with its different storage solutions, and make your application shine.

If you are an iOS developer looking to integrate your application with iCloud and to enhance it with data synchronization and backup, this book is for you. This book is also for those who simply want to know more about iCloud and the features it provides to client applications.

Before digging in, you should already know the basics of programming iOS, including proficiency in coding with Objective-C 2.0, working with view controllers, and using common data structures such as arrays and dictionaries. If you dont normally use them, I also suggest you refresh your knowledge of Notification Center both of which are used extensively throughout the book.

This book is an introduction to iCloud and how to use its APIs to add synchronization and data backup in your applications. Well cover the three main technologies that iCloud supports: key-value storage, document-based storage, and Core Data storage. I will illustrate the use of these APIs by showing how to build a Universal iOS app, Grocery, that keeps track of a shopping list.

The book starts with the simplest approach to synchronizing data with iCloud, key-value storage, and ends with the most advanced, Core Data. Unless you have previous experience with iCloud APIs,I suggest you read the book from start to finish and take the time to understand the concepts and techniques ofiCloud development as they are introduced. Throughout the book, you will be invited to build and run the Grocery application as it is being developed. You should consider these as conceptual check pointsopportunities to ask yourself whether you have a clear understanding of whats been described in the previous sections.

Objective-C is a verbose language. You will find snippets in this book that do not appear to be conventionally formatted, in the way you would expect them to appear in Xcode. Thats because of the lengths of many of the names used in iCloud programming, such as those for the various notifications the service provides. Some of these are lengthy and cannot be broken on two different lines. I have tried as much as possible to preserve Cocoa conventions, but sometimes the size of the page rules.

This book has a companion website at http://www.icloudfordevelopers.com and a mailing list in which news will be announced.

In this book we are going to build a real application. You will learn how to set it up and configure it correctly. But its not possible to test an iCloud-enabled application on the Device Simulator. This means that to get the most out of the book, youll need a pair of real devices, such as an iPhone and an iPad, both with iOS 6 installed and with iCloud correctly configured and enabled.