Objective-C Fundamentals

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Important protocols 161 Listing 7.13 NSXMLParser methods - (void)parser:(NSXMLParser *)parser didEndElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName { NSLog(@"Found an element named: %@ with a value of: %@", elementName, element); } This method is called when the parser sees anything between an element’s beginning and end. You use this entry point as a way to collect all the characters that are between an XML element beginning and ending: you call the appendString method on the NSMutableString (listing 7.14). By doing this every time the parser:foundCharacters: method is called, by the time the parser:didEndElement method is called, the NSMutableString will be complete. In this method, you first make sure you’ve initialized your NSMutableString element, and then you append the string you’ve provided, shown in the next listing. Listing 7.14 NSXMLParser methods - (void)parser:(NSXMLParser *)parser foundCharacters:(NSString *)string { if (element == nil) element = [[NSMutableString alloc] init]; [element appendString:string]; } Now all that’s left to do is create an instance of your parser and watch it go. Go to Parser_ProjectAppDelegate.m and add the code shown in the following listing into the already existing method. Listing 7.15 Initializing the Parser - (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions { self.window.rootViewController = self.viewController; [self.window makeKeyAndVisible]; } Parser *parser = [[Parser alloc] init]; return YES; If you run the application and bring up the terminal window (Shift-Command-R), the output shown in the following listing should be generated.
162 CHAPTER 7 Protocols Listing 7.16 Parser output Parser_Project[57815:207] Started Element Author Parser_Project[57815:207] Started Element name Parser_Project[57815:207] Found an element named: name with a value of: Collin Ruffenach Parser_Project[57815:207] Started Element age Parser_Project[57815:207] Found an element named: age with a value of: 23 Parser_Project[57815:207] Started Element gender Parser_Project[57815:207] Found an element named: gender with a value of: male Parser_Project[57815:207] Started Element Books Parser_Project[57815:207] Started Element Book Parser_Project[57815:207] Started Element title Parser_Project[57815:207] Found an element named: title with a value of: <strong>Objective</strong> C for the iPhone Parser_Project[57815:207] Started Element year Parser_Project[57815:207] Found an element named: year with a value of: 2010 Parser_Project[57815:207] Started Element level Parser_Project[57815:207] Found an element named: level with a value of: intermediate Parser_Project[57815:207] Found an element named: Book with a value of: intermediate Parser_Project[57815:207] Found an element named: Books with a value of: intermediate Parser_Project[57815:207] Found an element named: Author with a value of: intermediate You can see that, using the NSXMLParser delegate methods, you successfully parsed all of the information in your XML file. From here you could create <strong>Objective</strong>-C objects to represent the XML and use it throughout your application. XML processing is a vital part of most applications that get their content from some kind of web source: Twitter clients, News clients, or YouTube. 7.4 Summary Protocols are regularly seen when developing using UIKit and Core Foundation for the iPhone. They’re one of the foundation design decisions for most of the classes Apple provides. With attentive coding, protocols can make your application efficient and error proof. We looked at defining your own protocol for a variety of reasons, conforming to protocols, and some specific popular protocols from the iPhone SDK. These protocols are also great to use when creating code you want to reuse. Through a proper understanding and implementation of the protocol design method, you can ensure a welldesigned application. In chapter 8, we look at how you can define your classes to have dynamic typing. Dynamic typing is an important principle to apply when considering memory for your applications. It’s used in many protocol implementations, and a good grasp of dynamic styping will further your understanding of protocol design.
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Christopher K. Fairbairn Johannes F
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Objective-C Fundamentals CHRISTOPHE
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PART 1 brief contents GETTING START
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viii CONTENTS 1.5 Compiling the Coi
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x CONTENTS 5.4 Declared properties
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xii CONTENTS PART 3 MAKING MAXIMUM
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preface Having been involved in the
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ACKNOWLEDGMENTS xvii Christopher wo
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ABOUT THIS BOOK xix skills. There
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author online Purchase of Objective
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Part 1 Getting started with Objecti
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4 CHAPTER 1 Building your first iOS
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10 CHAPTER 1 Building your first iO
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Data types, variables, and constant
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30 CHAPTER 2 Data types, variables,
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56 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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Page 138 and 139: Creating and destroying objects 115
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Page 148 and 149: Subclassing 125 the only class you
Page 150 and 151: Adding new instance variables 127 s
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Page 154 and 155: Overriding methods 131 } return gen
Page 156 and 157: Overriding methods 133 } "for $%@ p
Page 158 and 159: Class clusters 135 Figure 6.2 Graph
Page 160 and 161: Categories 137 This code tells the
Page 162 and 163: Subclassing in your demo applicatio
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Page 166 and 167: Summary 143 6.8 Summary Object-orie
Page 168 and 169: Defining a protocol 145 Mastering t
Page 170 and 171: Implementing a protocol 147 7.2.1 C
Page 172 and 173: Implementing a protocol 149 Listing
Page 174 and 175: Important protocols 151 iPhone UIKi
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Page 178 and 179: Important protocols 155 Any table v
Page 180 and 181: Important protocols 157 or in table
Page 182 and 183: Important protocols 159 For s
Page 186 and 187: Dynamic typing and runtime type inf
Page 188 and 189: Static vs. dynamic typing 165 If yo
Page 190 and 191: How messaging works 167 Messages ar
Page 192 and 193: How messaging works 169 8.3.2 Handl
Page 194 and 195: Runtime type information 171 The if
Page 196 and 197: Runtime type information 173 8.4.3
Page 198 and 199: Practical uses of runtime type intr
Page 200 and 201: Memory management This chapter cove
Page 202 and 203: Reference counting 179 Figure 9.1 A
Page 204 and 205: Reference counting 181 the object i
Page 206 and 207: Reference counting 183 Keep yoursel
Page 208 and 209: Autorelease pools 185 Ideally, you
Page 210 and 211: Autorelease pools 187 With knowledg
Page 212 and 213: Autorelease pools 189 i * 1000 + j]
Page 214 and 215: Memory zones 191 Memory zones have
Page 216 and 217: Responding to low-memory warnings 1
Page 222 and 223: Summary 199 addObserver:selector:na
Page 224 and 225: Part 3 Making maximum use of framew
Page 226 and 227: Error and exception handling This c
Page 228 and 229: NSError—handling errors the Cocoa
Page 230 and 231: Creating NSError objects 207 chapte
Page 232 and 233: 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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Objective-C Fundamentals

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