iOS 7 Programming Fundamentals: Objective-C, Xcode, and Cocoa Basics (2014)

Preface

After three editions of my book on programming iOS — Programming iOS 4 (May 2011), Programming iOS 5 (March 2012), and Programming iOS 6 (March 2013) — it is as if a friendly but powerful giant had ripped the book in two, just after the end of Part III (Chapter 13). There are nowtwo books:

§ This book, iOS 7 Programming Fundamentals, comprising chapters 1–13 of the earlier books.

§ The other book, Programming iOS 7, comprising chapters 14–40 of the earlier books.

The giant was friendly, because it was high time. Programming iOS 6 had grown to an unwieldy and forbidding 1150 pages. In fact, I had been begging for this giant even before Programming iOS 4 was published — indeed, before it was even conceived of. My original proposal to O’Reilly Media, back in early 2010, had been for a book to be called Fundamentals of Cocoa Programming, intended to cover very much the same material as the present book, iOS 7 Programming Fundamentals. But the proposal was accepted only on condition that it be extended to cover much more of Cocoa Touch (iOS) programming; so I complied and set to work on this longer project, and later, despite my impassioned pleas in the autumn of 2010, I was unable to persuade the publisher to break up the lengthy manuscript into two: by that time, all the king’s horses and all the king’s men could no longer crack Humpty Dumpty apart.

The new situation, therefore, is just what I always wanted in the first place — but not quite, because what I most desired was a single book in two volumes. My idea was that the books would have the same title, distinguished as Volume I and Volume II, with successive numbering of pages and chapters: if Volume I ended, say, with Chapter 13 and page 400, then Volume II would start with Chapter 14 and page 401. To this delightfully Victorian extreme, I’m sorry to say, O’Reilly Media were implacably opposed.

Thus, Programming iOS 7, though it starts with its own Chapter 1 and page 1, nevertheless still picks up exactly where iOS 7 Programming Fundamentals leaves off. They complement and supplement one another. Those who desire a complete grounding in the knowledge needed to begin writing iOS apps with a solid and rigorous understanding of what they are doing and where they are heading will, I hope, obtain both books. At the same time, the two-book architecture should, I believe, render the size and scope of each book individually more acceptable and attractive to more readers.

Those who feel that they know already all there is to know about C, Objective-C, Xcode, and the linguistic and architectural basis of the Cocoa framework, or who are content to pick up such underpinnings as they go along, need no longer (as some in the past have done) complain that the book is occupied with 13 preliminary chapters before the reader starts really writing any significant iOS code, because those 13 chapters have now been abstracted into a separate volume, iOS 7 Programming Fundamentals, and the other book, Programming iOS 7, now begins, like Homer’sIliad, in the middle of the story, with the reader jumping with all four feet into views and view controllers, and with a knowledge of the language and the Xcode IDE already presupposed. And if such a reader subsequently changes his or her mind and decides that a thorough grounding in those underpinnings might in fact be desirable, iOS 7 Programming Fundamentals will still be available and awaiting study.

As for this book, iOS 7 Programming Fundamentals itself, it is the prodigal child, the book I originally wanted to write but which was then subsumed during three editions into the larger world of Programming iOS 4, Programming iOS 5, and Programming iOS 6. Now it is home again, where it belongs, in a volume of its own. Its three parts teach the underlying basis of all iOS programming:

§ Part I introduces the Objective-C language, starting with C (which constitutes much more of practical Objective-C than many beginners realize) and then building up to the object-oriented concepts and mechanics of classes and instances.

§ Part II takes a break from language and turns to Xcode, the world in which all iOS programming ultimately takes place. It explains what an Xcode project is and how it is transformed into an app, and how to work comfortably and nimbly with Xcode to consult the documentation and to write, navigate, and debug code, as well as how to bring your app through the subsequent stages of running on a device and submission to the App Store. There is also a very important chapter on nibs and the nib editor (Interface Builder), including outlets and actions as well as the mechanics of nib loading; however, such specialized topics as autolayout constraints in the nib are postponed to the other book.

§ Part III returns to Objective-C, this time from the point of view of the Cocoa Touch framework. Cocoa provides important foundational classes and adds linguistic and architectural devices such as categories, protocols, delegation, and notifications, as well as the pervasive responsibilities of memory management. Key–value coding and key–value observing are also discussed here.

The reader of this book will thus get a thorough grounding in the fundamental knowledge and techniques that any good iOS programmer needs. The book itself doesn’t show how to write any particularly interesting iOS apps (though it is backed by dozens of example projects that you can download from my GitHub site, http://github.com/mattneub/Programming-iOS-Book-Examples), but it does constantly use my own real apps and real programming situations to illustrate and motivate its explanations. And then you’ll be ready for Programming iOS 7, of course!

Versions

This book is geared to iOS 7 and Xcode 5. In general, only very minimal attention is given to earlier versions of iOS and Xcode. It is not my intention to embrace in this book any detailed knowledge about earlier versions of the software, which is, after all, readily and compendiously available in my earlier books. There are, nevertheless, a few words of advice about backwards compatibility, and now and then I will call out a particularly noteworthy change from earlier versions. For example, it has been hard to refrain from pointing out the confusing accretions of interface and terminology caused by the changes in how the status bar works and in the sizes of icons and launch images.

Xcode 5 no longer offers the user, creating a new app project from one of the project templates, an option as to whether or not to use Automatic Reference Counting (ARC), the compiler-based manual memory management technology that has made life so much easier for iOS programmers in recent years. ARC is simply turned on by default. Therefore, this book assumes from the outset that you are using ARC. I do still quite often distinguish the ARC compiler behavior from the non-ARC compiler behavior, but I no longer describe what the non-ARC behavior is, except inChapter 12 where I still explain what ARC does by describing what you would have to do if you weren’t using it.

Xcode also no longer provides a template-based option as to whether or not to use a storyboard. All projects (except the Empty Application template) come with a main storyboard, and there is no option to use a main .xib file instead. Taking my cue from this, I have adapted my teaching style to assume that storyboards are primary and that you’ll usually be using one. I do also show how to construct a project whose nibs come entirely from .xib files; this is more work than in the past, because you can’t do it simply by unchecking a checkbox in the template-creation dialog.

I have also embraced, often without much fanfare, the various other iOS 7 and Xcode 5 innovations. Apple has clearly set out, with this generation of their software, to make iOS programming easier and more pleasant than ever; and by and large they have succeeded. Such innovations as modules and autolinking, asset catalogs, the Accounts preference pane, and the Test navigator contrive to make your life far more comfortable, and I simply assume as a matter of course that you will want to use them.

From the Programming iOS 4 Preface

The popularity of the iPhone, with its largely free or very inexpensive apps, and the subsequent popularity of the iPad, have brought and will continue to bring into the fold many new programmers who see programming for these devices as worthwhile and doable, even though they may not have felt the same way about OS X. Apple’s own annual WWDC developer conventions have reflected this trend, with their emphasis shifted from OS X to iOS instruction.

The widespread eagerness to program iOS, however, though delightful on the one hand, has also fostered a certain tendency to try to run without first learning to walk. iOS gives the programmer mighty powers that can seem as limitless as imagination itself, but it also has fundamentals. I often see questions online from programmers who are evidently deep into the creation of some interesting app, but who are stymied in a way that reveals quite clearly that they are unfamiliar with the basics of the very world in which they are so happily cavorting.

It is this state of affairs that has motivated me to write this book, which is intended to ground the reader in the fundamentals of iOS. I love Cocoa and have long wished to write about it, but it is iOS and its popularity that has given me a proximate excuse to do so. Here I have attempted to marshal and expound, in what I hope is a pedagogically helpful and instructive yet ruthlessly Euclidean and logical order, the principles on which sound iOS programming rests, including a good basic knowledge of Objective-C (starting with C itself) and the nature of object-oriented programming, advice on the use of the tools, the full story on how Cocoa objects are instantiated, referred to, put in communication with one another, and managed over their lifetimes, and a survey of the primary interface widgets and other common tasks. My hope, as with my previous books, is that you will both read this book cover to cover (learning something new often enough to keep you turning the pages) and keep it by you as a handy reference.

This book is not intended to disparage Apple’s own documentation and example projects. They are wonderful resources and have become more wonderful as time goes on. I have depended heavily on them in the preparation of this book. But I also find that they don’t fulfill the same function as a reasoned, ordered presentation of the facts. The online documentation must make assumptions as to how much you already know; it can’t guarantee that you’ll approach it in a given order. And online documentation is more suitable to reference than to instruction. A fully written example, no matter how well commented, is difficult to follow; it demonstrates, but it does not teach.

A book, on the other hand, has numbered chapters and sequential pages; I can assume you know C before you know Objective-C for the simple reason that Chapter 1 precedes Chapter 2. And along with facts, I also bring to the table a degree of experience, which I try to communicate to you. Throughout this book you’ll see me referring to “common beginner mistakes”; in most cases, these are mistakes that I have made myself, in addition to seeing others make them. I try to tell you what the pitfalls are because I assume that, in the course of things, you will otherwise fall into them just as naturally as I did as I was learning. You’ll also see me construct many examples piece by piece or extract and explain just one tiny portion of a larger app. It is not a massive finished program that teaches programming, but an exposition of the thought process that developed that program. It is this thought process, more than anything else, that I hope you will gain from reading this book.

Conventions Used in This Book

The following typographical conventions are used in this book:

Italic

Indicates new terms, URLs, email addresses, filenames, and file extensions.

Constant width

Used for program listings, as well as within paragraphs to refer to program elements such as variable or function names, databases, data types, environment variables, statements, and keywords.

Constant width bold

Shows commands or other text that should be typed literally by the user.

Constant width italic

Shows text that should be replaced with user-supplied values or by values determined by context.

TIP

This icon signifies a tip, suggestion, or general note.

WARNING

This icon indicates a warning or caution.