Aut lego vel scribo; doceo scrutorve sophian.

Sedulius Scottus

This book, now in its fourth edition, has grown in size to encompass the growth in its subject, until it can grow no more. The previous editions — Programming iOS 4 (May 2011), Programming iOS 5 (March 2012), and Programming iOS 6 (March 2013) — were approximately 800 pp., 950 pp., and 1150 pp. in length, respectively, not because I had more to say each time, but because Apple, as it added features to iOS 4 to make iOS 5, and to iOS 5 to make iOS 6, had given me more to describe.

Now iOS 7 has come along with even more new features, and drastic action was needed. Accordingly, the book has been ripped violently but neatly in two — neatly, because there was already a perfectly natural place to do the ripping, namely right after the end of what used to be Part III (Chapter 13). There are now two books:

The truth is that this is a division I had wanted to make 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 iOS 7 Programming Fundamentals covers now. 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 this book, Programming iOS 7, now begins, like Homer’s Iliad, 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.

Moreover, the existence of iOS 7 Programming Fundamentals means that I, as author and teacher, can make the same assumption in this edition about you, as reader and student, that I made in previous editions — namely, that you have a command of the material in that book. If you find yourself mystified by terminology or concepts used in this book, then it might be wise to stop reading it and take up iOS 7 Programming Fundamentals first! In it, I explain such things as:

  • The Objective-C language, starting with C and building up to the object-oriented concepts and mechanics of classes and instances in Objective-C itself.
  • Xcode, the world in which all iOS programming ultimately takes place, including 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, some additional important nib-related topics, such as autolayout constraints and storyboard segues, are discussed in this book.)
  • The Cocoa Touch framework, which 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, plus key–value coding and key–value observing.

With those basics having been laid down in iOS 7 Programming Fundamentals, this book, Programming iOS 7, assumes that you already know Objective-C and how to work with Xcode to edit code and nibs, make properties and outlets and actions, and so forth, and proceeds to explain the constituents of practical iOS app construction:

  • Part I describes views, the fundamental units of an iOS app’s interface. Views are what the user can see and touch in an iOS app. To make something appear before the user’s eyes, you need a view. To let the user interact with your app, you need a view. This part of the book explains how views are created, arranged, drawn, layered, animated, and touched.
  • Part II starts by discussing view controllers. Perhaps the most remarkable and important feature of iOS programming, view controllers enable views to come and go coherently within the interface, thus allowing a single-windowed app running on what may be a tiny screen to contain multiple screens of material. This part of the book talks about all the ways in which view controllers can be manipulated in order to make their views appear. It also describes every kind of view provided by the Cocoa framework — the built-in “widgets” with which you’ll construct an app’s interface.
  • Part III surveys many of the secondary frameworks provided by iOS. These are clumps of code, sometimes with built-in interface, that are not part of your app by default, but are there for the asking if you need them, allowing you to work with such things as sound, video, user libraries, mail, maps, and the device’s sensors.
  • Part IV wraps up the book with some miscellaneous but important topics: files, networking, threading, and how to implement Undo and Redo.
  • Appendix A summarizes the most important lifetime event messages sent to your app delegate.

Someone who has read this book (and who, it goes without saying, is conversant with the material in iOS 7 Programming Fundamentals) will, I believe, be capable of writing a real-life iOS app, and to do so with a clear understanding of what he or she is doing and where the app is going as it grows and develops. 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,, but it does constantly use my own real apps and real programming situations to illustrate and motivate its explanations.

Just as important, this book is intended to prepare you for your own further explorations. In the case of some topics, especially in Part III and Part IV, I guide you past the initial barrier of no knowledge into an understanding of the topic, its concepts, its capabilities, and its documentation, along with some code examples; but the topic itself may be so huge that there is room only to introduce it here. Your feet, nevertheless, will now be set firmly on the path, and you will know enough that you can now proceed further down that path on your own whenever the need or interest arises.

Indeed, there is always more to learn about iOS. iOS is vast! It is all too easy to find areas of iOS that have had to be ruled outside the scope of this book. In Part IV, for example, I peek at Core Data, and demonstrate its use in code, but a true study of Core Data would require an entire book of its own (and such books exist); so, having opened the door, I quickly close it again, lest this book suddenly double in size. By the same token, many areas of iOS are not treated at all in this book:

An open source C library for drawing, including 3D drawing, that takes full advantage of graphics hardware. This is often the most efficient way to draw, especially when animation is involved. iOS incorporates a simplified version of OpenGL called OpenGL ES. See Apple’s OpenGL Programming Guide for iOS. Open GL interface configuration, texture loading, shading, and calculation are simplified by the GLKit framework; see the GLKit Framework Reference.
Sprite Kit
New in iOS 7, Sprite Kit provides a built-in framework for designing 2D animated games.
Certain computation-intensive processes will benefit from the vector-based Accelerate framework. See the vDSP Programming Guide.
Game Kit
The Game Kit framework covers three areas that can enhance your user’s game experience: Wireless or Bluetooth communication directly between devices (peer-to-peer); voice communication across an existing network connection; and Game Center, which facilitates these and many other aspects of interplayer communication, such as posting and viewing high scores and setting up combinations of players who wish to compete. See the Game Kit Programming Guide.
The iAD framework lets your free app attempt to make money by displaying advertisements provided by Apple. See the iAD Programming Guide.
Your app may represent a subscription to something like a newspaper or magazine. See the Newsstand Kit Framework Reference.
See the “Printing” chapter of the Drawing and Printing Guide for iOS.
This book does not discuss security topics such as keychains, certificates, and encryption. See the Security Overview and the Security framework.
VoiceOver assists visually impaired users by describing the interface aloud. To participate, views must be configured to describe themselves usefully. Built-in views already do this to a large extent, and you can extend this functionality. See the Accessibility Programming Guide for iOS.
The Core Telephony framework lets your app get information about a particular cellular carrier and call.
Pass Kit
The Pass Kit framework allows creation of downloadable passes to go into the user’s Passbook app. See the Passbook Programming Guide.
External accessories
The user can attach an external accessory to the device, either directly via USB or wirelessly via Bluetooth. Your app can communicate with such an accessory. See External Accessory Programming Topics.


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 backward 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 confusion caused by the changes in how the status bar works, or in the meaning of tintColor, or the nightmarish way in which your perfectly viable iOS 6 project, when recompiled against iOS 7, will try to resize and reposition its views incorrectly, underlapping the navigation bar.)

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.

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 assume that you know how to make and work with a .xib file when you need one, as this is explained in iOS 7 Programming Fundamentals.)

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. For example, modules and autolinking have made it much simpler than in the past to work with additional frameworks, and I simply assume as a matter of course that you will be using them; thus, when telling you what to do in order to employ a certain framework, I give simply the relevant @import command. Similarly, in discussing drawing and images in Chapter 2, I naturally steer you toward the use of asset catalogs.


My thanks go first and foremost to the people at O’Reilly Media who have made writing a book so delightfully easy: Rachel Roumeliotis, Sarah Schneider, Kristen Brown, and Adam Witwer come particularly to mind. And let’s not forget my first and long-standing editor, Brian Jepson, who had nothing whatever to do with this edition, but whose influence is present throughout.

As in the past, I have been greatly aided by some fantastic software, whose excellences I have appreciated at every moment of the process of writing this book. I should like to mention, in particular:

The book was typed and edited entirely on my faithful Unicomp Model M keyboard (, without which I could never have done so much writing over so long a period so painlessly. For more about my physical work environment, see

From the Programming iOS 4 Preface

A programming framework has a kind of personality, an overall flavor that provides an insight into the goals and mindset of those who created it. When I first encountered Cocoa Touch, my assessment of its personality was: “Wow, the people who wrote this are really clever!” On the one hand, the number of built-in interface widgets was severely and deliberately limited; on the other hand, the power and flexibility of some of those widgets, especially such things as UITableView, was greatly enhanced over their OS X counterparts. Even more important, Apple created a particularly brilliant way (UIViewController) to help the programmer make entire blocks of interface come and go and supplant one another in a controlled, hierarchical manner, thus allowing that tiny iPhone display to unfold virtually into multiple interface worlds within a single app without the user becoming lost or confused.

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 and elements on which sound iOS programming rests. 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 views before you know view controllers for the simple reason that Part I precedes Part II. 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 find 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:

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.


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