www.it-ebooks.info For your convenience Apress has placed some of the front matter material after the index. Please use the Bookmarks and Contents at a Glance links to access them. www.it-ebooks.info v Contents at a Glance About the Authors �������������������������������������������������������������������������������������������������������������� xxi About the Technical Reviewers ��������������������������������������������������������������������������������������� xxiii Chapter 1: Welcome to the Jungle ■ �������������������������������������������������������������������������������������1 Chapter 2: Appeasing the Tiki Gods ■ ���������������������������������������������������������������������������������11 Chapter 3: Handling Basic Interaction ■ �����������������������������������������������������������������������������43 Chapter 4: More User Interface Fun ■ ��������������������������������������������������������������������������������69 Chapter 5: Autorotation and Autosizing ■ ������������������������������������������������������������������������115 Chapter 6: Multiview Applications ■ ��������������������������������������������������������������������������������139 Chapter 7: Tab Bars and Pickers ■ �����������������������������������������������������������������������������������169 Chapter 8: Introduction to Table Views ■ �������������������������������������������������������������������������221 Chapter 9: Navigation Controllers and Table Views ■ �������������������������������������������������������269 Chapter 10: Storyboards ■ ������������������������������������������������������������������������������������������������341 Chapter 11: iPad Considerations ■ �����������������������������������������������������������������������������������367 Chapter 12: Application Settings and User Defaults ■ ������������������������������������������������������397 Chapter 13: Basic Data Persistence ■ ������������������������������������������������������������������������������435 Chapter 14: Hey! You! Get onto iCloud! ■ �������������������������������������������������������������������������481 www.it-ebooks.info vi Contents at a Glance Chapter 15: Grand Central Dispatch, Background Processing, and You ■ ������������������������511 Chapter 16: Drawing with Quartz and OpenGL ■ ��������������������������������������������������������������545 Chapter 17: Taps, Touches, and Gestures ■ ����������������������������������������������������������������������585 Chapter 18: Where Am I? Finding Your Way with Core Location and Map Kit ■ ���������������619 Chapter 19: Whee! Gyro and Accelerometer! ■ ����������������������������������������������������������������637 Chapter 20: The Camera and Photo Library ■ �������������������������������������������������������������������667 Chapter 21: Collection View ■ ������������������������������������������������������������������������������������������677 Chapter 22: Application Localization ■ �����������������������������������������������������������������������������691 Appendix A: Where to Next? ■ ������������������������������������������������������������������������������������������717 Index ���������������������������������������������������������������������������������������������������������������������������������725 www.it-ebooks.info 1 Chapter 1 Welcome to the Jungle So, you want to write iPhone, iPod touch, and iPad applications? Well, we can’t say that we blame you. iOS, the core software of all of these devices, is an exciting platform that has been seeing explosive growth since it first came out in 2007. The rise of the mobile software platform means that people are using software everywhere they go. With the release of iOS 6, and the latest incarnation of the iOS software development kit (SDK), things have only gotten better and more interesting. What This Book Is This book is a guide to help you get started down the path to creating your own iOS applications. Our goal is to get you past the initial difficulties, to help you understand the way iOS applications work and how they are built. As you work your way through this book, you will create a number of small applications, each designed to highlight specific iOS features and to show you how to control or interact with those features. If you combine the foundation you’ll gain through this book with your own creativity and determination, and then add in the extensive and well-written documentation provided by Apple, you’ll have everything you need to build your own professional iPhone and iPad applications. Tip Dave, Jack, Jeff, and Fredrik have set up a forum for this book. It’s a great place to meet like-minded folks, get your questions answered, and even answer other people’s questions. The forum is at http://forum.learncocoa.org. Be sure to check it out! What You Need Before you can begin writing software for iOS, you’ll need a few items. For starters, you’ll need an Intel-based Macintosh, running Lion (OS X 10.7) or later. Any recent Intel-based Macintosh computer—laptop or desktop—should work just fine. www.it-ebooks.info 2 CHAPTER 1: Welcome to the Jungle You’ll also need to sign up to become a registered iOS developer. Apple requires this step before you’re allowed to download the iOS SDK. To sign up as a developer, just navigate to http://developer.apple.com/ios/. That will bring you to a page similar to the one shown in Figure 1-1. Figure 1-1. Apple’s iOS Dev Center website First, click on Log in. You’ll be prompted for your Apple ID. If you don’t have an Apple ID, click Join now, create one, and then log in. Once you are logged in, you’ll be taken to the main iOS development page. Not only will you see a link to the SDK download, but you’ll also find links to a wealth of documentation, videos, sample code, and the like—all dedicated to teaching you the finer points of iOS application development. The most important tool you’ll be using to develop iOS applications is called Xcode. Xcode is Apple’s integrated development environment (IDE). Xcode includes tools for creating and debugging source code, compiling applications, and performance tuning the applications you’ve written. You can download Xcode from the Mac App Store, which you can access from your Mac’s Apple menu. www.it-ebooks.info 3CHAPTER 1: Welcome to the Jungle As the versions of the SDK and Xcode evolve, the mechanism for downloading them will also change. Starting with the release of Xcode 4.3, Apple has been publishing the current “stable” version of Xcode and the iOS SDK on the Mac App Store, while simultaneously often providing developers the ability to download preview versions of upcoming releases from their developer site. Bottom line: you want to download the latest released (non-beta) version of Xcode and the iOS SDK, so use the Mac App Store. This book has been written to work with the latest version of the SDK. In some places, we have chosen to use new functions or methods introduced with iOS 6 that may prove incompatible with earlier versions of the SDK. We’ll be sure to point those situations out as they arise in this book. Be sure to download the latest and greatest source code archives from http://iphonedevbook.com or from the book’s forum at http://forum.learncocoa.org. We’ll update the code as new versions of the SDK are released, so be sure to check the site periodically. Developer Options The free SDK download option includes a simulator that will allow you to build and run iPhone and iPad apps on your Mac. This is perfect for learning how to program for iOS. However, the simulator does not support many hardware-dependent features, such as the accelerometer and camera. Also, the free option will not allow you to download your applications onto your actual iPhone or other device, and it does not give you the ability to distribute your applications on Apple’s App Store. For those capabilities, you’ll need to sign up for one of the other options, which aren’t free: The Standard program costs $99/year. It provides a host of development tools  and resources, technical support, distribution of your application via Apple’s App Store, and, most important, the ability to test and debug your code on an iOS device, rather than just in the simulator. The Enterprise program costs $299/year. It is designed for companies  developing proprietary, in-house iOS applications. For more details on these programs, visit http://developer.apple.com/programs/ios and http://developer.apple.com/programs/ios/enterprise to compare the two. Because iOS supports an always-connected mobile device that uses other companies’ wireless infrastructure, Apple has needed to place far more restrictions on iOS developers than it ever has on Mac developers (who are able—at the moment anyway—to write and distribute programs with absolutely no oversight or approval from Apple). Even though the iPod touch and the Wi-Fi-only versions of the iPad don’t use anyone else’s infrastructure, they’re still subject to these same restrictions. Apple has not added restrictions to be mean, but rather as an attempt to minimize the chances of malicious or poorly written programs being distributed that could degrade performance on the shared network. Developing for iOS may appear to present a lot of hoops to jump through, but Apple has expended quite an effort to make the process as painless as possible. And also consider that $99 is still much less than buying, for example, Visual Studio, which is Microsoft’s software development IDE. SDK VERSIONS AND SOURCE CODE FOR THE EXAMPLES www.it-ebooks.info 4 CHAPTER 1: Welcome to the Jungle This may seem obvious, but you’ll also need an iPhone, iPod touch, or iPad. While much of your code can be tested using the iOS simulator, not all programs can be. And even those that can run on the simulator really need to be thoroughly tested on an actual device before you ever consider releasing your application to the public. Note If you are going to sign up for the Standard or Enterprise program, you should do it right now. The approval process can take a while, and you’ll need that approval to be able to run your applications on an actual device. Don’t worry, though, because all the projects in the first several chapters and the majority of the applications in this book will run just fine on the iOS simulator. What You Need to Know This book assumes that you already have some programming knowledge. It assumes that you understand the fundamentals of object-oriented programming (you know what objects, loops, and variables are, for example). It also assumes that you are familiar with the Objective-C programming language. Cocoa Touch, the part of the SDK that you will be working with through most of this book, uses the latest version of Objective-C, which contains several new features not present in earlier versions. But don’t worry if you’re not familiar with the more recent additions to the Objective-C language. We highlight any of the new language features we take advantage of, and explain how they work and why we are using them. You should also be familiar with iOS itself, as a user. Just as you would with any platform for which you wanted to write an application, get to know the nuances and quirks of the iPhone, iPad, or iPod touch. Take the time to get familiar with the iOS interface and with the way Apple’s iPhone and/or iPad applications look and feel. NEW TO OBJECTIVE-C? If you have not programmed in Objective-C before, here are a few resources to help you get started: Check out • Learn Objective-C on the Mac: For OS X and iOS (2nd edition, Apress, 2012):, an excellent and approachable introduction to Objective-C by Mac-programming experts Scott Knaster, Waqar Malik, and Mark Dalrymple: http://www.apress.com/book/view/9781430241881. See Apple’s introduction to the language, Learning Objective-C: A Primer.• Take a look at • The Objective-C Programming Language, a very detailed and extensive description of the language and a great reference guide. The last two are available from http://developer.apple.com/library/ios/navigation/. That last one is also available as a free download from iBooks on your iPhone, iPod touch, or iPad. It’s perfect for reading on the go! Apple has released several developer titles in this format, and we hope that more are on the way. Search for “Apple developer publications” in iBooks to find them. www.it-ebooks.info 5CHAPTER 1: Welcome to the Jungle What’s Different About Coding for iOS? If you have never programmed in Cocoa or its predecessors NeXTSTEP or OpenStep, you may find Cocoa Touch—the application framework you’ll be using to write iOS applications—a little alien. It has some fundamental differences from other common application frameworks, such as those used when building .NET or Java applications. Don’t worry too much if you feel a little lost at first. Just keep plugging away at the exercises, and it will all start to fall into place after a while. If you have written programs using Cocoa or NeXTSTEP, a lot in the iOS SDK will be familiar to you. A great many classes are unchanged from the versions that are used to develop for OS X. Even those that are different tend to follow the same basic principles and similar design patterns. However, several differences exist between Cocoa and Cocoa Touch. Regardless of your background, you need to keep in mind some key differences between iOS development and desktop application development. These differences are discussed in the following sections. Only One Active Application On iOS, only one application can be active and displayed on the screen at any given time. Since iOS 4, applications have been able to run in the background after the user presses the “home” button, but even that is limited to a narrow set of situations, and you must code for it specifically. When your application isn’t active or running in the background, it doesn’t receive any attention whatsoever from the CPU, which will wreak havoc with open network connections and the like. iOS allows background processing, but making your apps play nicely in this situation will require some effort on your part. Only One Window Desktop and laptop operating systems allow many running programs to coexist, each with the ability to create and control multiple windows. However, iOS gives your application just one “window” to work with. All of your application’s interaction with the user takes place inside this one window, and its size is fixed at the size of the screen. Limited Access Programs on a computer pretty much have access to everything the user who launched them does. However, iOS seriously restricts what your application can access. You can read and write files only from the part of iOS’s file system that was created for your application. This area is called your application’s sandbox. Your sandbox is where your application will store documents, preferences, and every other kind of data it may need to retain. Your application is also constrained in some other ways. You will not be able to access low-number network ports on iOS, for example, or do anything else that would typically require root or administrative access on a desktop computer. www.it-ebooks.info 6 CHAPTER 1: Welcome to the Jungle Limited Response Time Because of the way it is used, iOS needs to be snappy, and it expects the same of your application. When your program is launched, you need to get your application open, preferences and data loaded, and the main view shown on the screen as fast as possible—in no more than a few seconds. At any time when your program is running, it may have the rug pulled out from under it. If the user presses the home button, iOS goes home, and you must quickly save everything and quit. If you take longer than five seconds to save and give up control, your application process will be killed, regardless of whether you are finished saving. Note that since iOS 5, this situation has been ameliorated somewhat by the existence of new API that allows your app to ask for additional time to work when it’s about to go dark. Limited Screen Size The iPhone’s screen is really nice. When introduced, it was the highest resolution screen available on a consumer device, by far. But the iPhone display just isn’t all that big, and as a result, you have a lot less room to work with than on modern computers. The screen is just 320 × 480 on the first few iPhone generations, and was later doubled in both directions to 640 × 960 with the introduction of the iPhone 4’s retina display. This was recently increased further to 640 × 1136 on the iPhone 5. That sounds like a decent number of pixels, but keep in minde that these retina displays are crammed into pretty small form factors, so you can’t count on fitting more controls or anything like that. This has a big impact on the kinds of applications and interactivity you can offer on an iPhone. The iPad increases the available space a bit by offering a 1024 × 768 display, but even today, that’s not so terribly large. To give an interesting contrast, at the time of writing, Apple’s least expensive iMac supports 1920 × 1080 pixels, and its least expensive notebook computer, the 11-inch MacBook Air, supports 1366 × 768 pixels. On the other end of the spectrum, Apple’s largest current monitor, the 27-inch LED Cinema Display, offers a whopping 2560 × 1440 pixels. Note that the 3 rd generation iPad released in the spring of 2012 (which Apple confusingly calls the “new iPad” instead of incrementing the number from the previous iPad 2) actually doubles the screen resolution in both directions. But as with the retina iPhones, that 2048 × 1536 screen is in the same physical space as the old screen was, so you can’t really count on using those pixels the same way you would on a traditional screen. Limited System Resources Any old-time programmers who are reading this are likely laughing at the idea of a machine with at least 512MB of RAM and 16GB of storage being in any way resource-constrained, but it is true. Developing for iOS is not, perhaps, in exactly the same league as trying to write a complex spreadsheet application on a machine with 48KB of memory. But given the graphical nature of iOS and all it is capable of doing, running out of memory is very easy. The iOS devices available right now have either 512MB (iPhone 4, iPhone 4S, iPad 2), or 1024MB of physical RAM (iPhone 5, new iPad), though that will likely increase over time. Some of that memory is used for the screen buffer and by other system processes. Usually, no more than half of that www.it-ebooks.info [...]... regardless of whether the extension actually used for the file is xib or nib In fact, Apple still uses the terms nib and nib file throughout its documentation The gray vertical bar on the left edge of the graph paper is known as the dock The dock contains an icon for each top-level object in the nib file If you click the triangle-in-a-circle icon just to the right of the bottom of the dock, you’ll see... of the iOS development community has been phenomenal The SDK has continually evolved, with Apple releasing a steady stream of SDK updates Well, we’ve been busy, too! The second we found out about iOS SDK 6, we immediately went to work, updating every single project to ensure not only that the code compiles using the latest version of Xcode and the SDK, but also that each one takes advantage of the. .. the tail end of the jump bar is a pop-up that shows the methods and other symbols contained by the currently selected file The jump bar in Figure 2-14 shows the file BIDAppDelegate.m, with a submenu listing the symbols defined in that file Figure 2-14.  The Xcode editor pane showing the jump bar, with a source code file selected The submenu shows the list of methods in the selected file The jump bar is... What’s in the Nib File? As we mentioned earlier, the contents of the nib file are represented by icons or a list in the dock immediately to the left of the editor pane (see Figure 2-15) Every nib file starts off with the same two icons: File’s Owner and First Responder These two are created automatically and cannot be deleted Furthermore, they are visually separated from the objects you add to the nib... Builder Everything above the library but below the toolbar is known collectively as the inspector www.it-ebooks.info 32 CHAPTER 2: Appeasing the Tiki Gods The bottom half of the utility view is called the library pane, or just plain library The library is a collection of reusable items you can use in your own programs The four icons in the bar at the top of the library pane divide the library into four... View” section earlier in the chapter) or by pressing 1 Tip  The seven navigator configurations can be accessed using the keyboard shortcuts 1 to 7 The numbers correspond to the icons starting on the left, so 1 is the project navigator, 2 is the symbol navigator, and so on up to 7, which takes you to the log navigator The first item in the project navigator list bears the same name as your project—in... called previously, in the order they were called Click a method, and the associated code appears in the editor pane In the editor, there will be a second frame, where you can control the debugging process, display and modify data values, and access the low-level debugger A slider at the bottom of the debug navigator allows you to control the level of detail it tracks Slide to the extreme right to see... include the current file  To the right of the über menu are left and right arrows that take you back to the previous file and return to the next file, respectively  The jump bar includes a segmented pop-up that displays the files for the current project that can be displayed for the current editor In Figure 2-14, we’re in the source code editor, so we see all the source files in our project At the tail... that the iOS SDK contains some functionality that is not currently present in Cocoa or, at least, is not available on every Mac:  The iOS SDK provides a way for your application to determine the iOS device’s current geographic coordinates using Core Location  Most iOS devices have built-in cameras and photo libraries, and the SDK provides mechanisms that allow your application to access both  iOS. .. sounds, and movies Note  The items in the object library are primarily from the iOS UIKit, which is a framework of objects used to create an app’s user interface UIKit fulfills the same role in Cocoa Touch as AppKit does in Cocoa The two frameworks are similar conceptually, but because of differences in the platforms, there are obviously many differences between them On the other hand, the Foundation framework . supports 1 366 × 768 pixels. On the other end of the spectrum, Apple’s largest current monitor, the 27-inch LED Cinema Display, offers a whopping 2 560 × 1440. 1: Welcome to the Jungle As the versions of the SDK and Xcode evolve, the mechanism for downloading them will also change. Starting with the release of