Objective-C Fundamentals

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Hooking up the user interface 15 Now that you have the basic logic of the game developed, you must create the user interface in Xcode and connect it back to the code in the CoinTossView- Controller class. 1.4 Hooking up the user interface At this stage, you can determine from the CoinTossViewController class definition that the user interface should have at least two UILabel controls and that it should invoke the callHeads or callTails messages whenever the user wants to call the result of a new coin toss. You haven’t yet specified where on the screen the labels should be positioned or how the user requests that a coin toss be made. There are two ways to specify this kind of detail. The first is to write source code that creates the user interface controls, configures their properties such as font size and color, and positions them onscreen. This code can be time consuming to write, and you can spend a lot of your time trying to visualize how things look onscreen. A better alternative is to use Xcode, which allows you to visually lay out and configure your user interface controls and connect them to your source code. Most iOS project templates use this technique and typically include one or more *.xib files designed to visually describe the user interface. This project is no exception, so click the Coin- TossViewController.xib file in the Project Navigator pane and notice that the editor pane displays the contents of the file (figure 1.6). Along the left edge of the editor pane are some icons. Each icon represents an object that’s created when the game runs, and each has a tooltip that displays it name. The wireframe box labeled File’s Owner represents an instance of the CoinTossView- Controller class; the white rectangle represents the main view (or screen) of the application. Using Xcode, you can graphically configure the properties of these objects and create connections between them. 1.4.1 Adding controls to a view The first step in defining the user interface for your game is to position the required user interface controls onto the view. To add controls, find them in the Library window, which contains a catalog of available user interface controls, and drag and drop them onto the view. If the Library window isn’t visible, you can open it via the View > Utilities > Object Library menu option (Control-Option-Cmd-3). For the Coin Toss game, you require two Labels and two Rounded Rect Buttons, so drag two of each control onto the view. The process of dragging and dropping a control onto the view is shown in figure 1.7. After you drag and drop the controls onto the view, you can resize and adjust their positions to suit your aesthetics. The easiest way to change the text displayed on a button or label control is to double-click the control and begin typing. To alter other properties, such as font size and color, you can use the Attributes Inspector pane, which can be displayed via the View > Utilities > Attributes Inspector menu option (Alt-Cmd-4). While styling your view, you can refer back to figure 1.2 for guidance.
16 CHAPTER 1 Building your first iOS application Figure 1.6 The main Xcode window demonstrating the editing of a *.xib file. Along the left edge of the editor you can see three icons, each representing a different object or GUI component stored in the .xib file. With the controls positioned on the user interface, the only task left is to connect them to the code you previously wrote. Remember that the class defined in the Coin- TossViewController.h header file requires three things from the user interface: ■ ■ ■ Something to send the callHeads or callTails messages whenever the user wishes to initiate a new coin toss A UILabel to display the results of the latest coin toss (heads or tails) A UILabel to display the status of the latest coin toss (correct or incorrect)
Page 1 and 2: Christopher K. Fairbairn Johannes F
Page 4 and 5: Objective-C Fundamentals CHRISTOPHE
Page 6: PART 1 brief contents GETTING START
Page 9 and 10: viii CONTENTS 1.5 Compiling the Coi
Page 11 and 12: x CONTENTS 5.4 Declared properties
Page 13 and 14: xii CONTENTS PART 3 MAKING MAXIMUM
Page 16 and 17: preface Having been involved in the
Page 18 and 19: ACKNOWLEDGMENTS xvii Christopher wo
Page 20 and 21: ABOUT THIS BOOK xix skills. There
Page 22 and 23: author online Purchase of Objective
Page 24: Part 1 Getting started with Objecti
Page 27 and 28: 4 CHAPTER 1 Building your first iOS
Page 33 and 34: 10 CHAPTER 1 Building your first iO
Page 37: 14 CHAPTER 1 Building your first iO
Page 51 and 52: Data types, variables, and constant
Page 53 and 54: 30 CHAPTER 2 Data types, variables,
Page 79 and 80: 56 CHAPTER 3 An introduction to obj
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66 CHAPTER 3 An introduction to obj
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Storing data in collections This ch
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76 CHAPTER 4 Storing data in collec
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Creating classes This chapter cover
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Declaring the interface of a class
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Providing an implementation for a c
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Declared properties 109 - (Property
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Declared properties 111 Let’s bri
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Declared properties 113 Although @s
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Creating and destroying objects 115
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Using the class in the Rental Manag
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Summary 123 a number of rental prop
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Subclassing 125 the only class you
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Adding new instance variables 127 s
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Accessing existing instance variabl
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Overriding methods 131 } return gen
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Overriding methods 133 } "for $%@ p
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Class clusters 135 Figure 6.2 Graph
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Categories 137 This code tells the
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Subclassing in your demo applicatio
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Subclassing in your demo applicatio
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Summary 143 6.8 Summary Object-orie
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Defining a protocol 145 Mastering t
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Implementing a protocol 147 7.2.1 C
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Implementing a protocol 149 Listing
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Important protocols 151 iPhone UIKi
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Important protocols 153 executed. T
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Important protocols 155 Any table v
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Important protocols 157 or in table
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Important protocols 159 For s
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Important protocols 161 Listing 7.1
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Dynamic typing and runtime type inf
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Static vs. dynamic typing 165 If yo
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How messaging works 167 Messages ar
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How messaging works 169 8.3.2 Handl
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Runtime type information 171 The if
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Runtime type information 173 8.4.3
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Practical uses of runtime type intr
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Memory management This chapter cove
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Reference counting 179 Figure 9.1 A
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Reference counting 181 the object i
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Reference counting 183 Keep yoursel
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Autorelease pools 185 Ideally, you
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Autorelease pools 187 With knowledg
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Autorelease pools 189 i * 1000 + j]
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Memory zones 191 Memory zones have
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Responding to low-memory warnings 1
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Summary 199 addObserver:selector:na
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Part 3 Making maximum use of framew
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Error and exception handling This c
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NSError—handling errors the Cocoa
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Creating NSError objects 207 chapte
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Creating NSError objects 209 10.2.2
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Summary 211 10.3.2 Catching excepti
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Making your objects KVC-compliant 2
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Making your objects KVC-compliant 2
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Handling special cases 217 This que
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Filtering and matching with predica
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Sample application 225 rentingFor:2
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Summary 227 The core of the logic o
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Core Data history 229 Structured Qu
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Core Data objects 231 In Xcode you
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Core Data resources 233 careful to
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Building the PocketTasks applicatio
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Beyond the basics 251 How do you us
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Beyond the basics 253 All you do is
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Beyond the basics 255 attributeName
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Blocks and Grand Central Dispatch T
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The syntax of blocks 259 What if yo
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The syntax of blocks 261 change the
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The syntax of blocks 263 } [super d
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Performing work asynchronously 265
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Summary 275 more to learn about GCD
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Building an application, complete w
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Understanding NSLog 279 Figure 14.3
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Bringing memory leaks under control
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Bringing memory leaks under control
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Detecting zombies 285 (and the appl
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Summary 287 and its ease of use and
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Preparing your iOS device for devel
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Preparing your iOS device for devel
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appendix B The basics of C Througho
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Variable naming conventions 295 As
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Expressions 297 Table B.3 Relationa
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Expressions 299 B.2.4 Assignment op
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Conditional statements 301 based on
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Conditional statements 303 The gene
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Looping statements 305 Not as strai
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Looping statements 307 One importan
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Looping statements 309 As in a do l
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Summary 311 CONTINUE The continue s
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A short history of Objective-C 313
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The iPhone SDK: Safari 315 C.2 Alte
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The iPhone SDK: Safari 317 C.3.2 ha
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The iPhone SDK: Safari 319 It’s i
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Scripting languages: Lua and Ruby 3
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Mono (.NET) 323 the iOS platform. F
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Summary 325 Xamarin announced a fol
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index Symbols ^ operator 298 - oper
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INDEX 329 application-specific quer
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INDEX 331 collections (continued) e
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INDEX 333 E e character 35 editButt
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INDEX 335 iOS Developer account 9 i
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INDEX 337 mutableCopyWithZone 190 M
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INDEX 339 Organizer window 291 over
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INDEX 341 setFlag 164 setNilValueFo
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INDEX 343 vardic method 75 variable
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