Objective-C Fundamentals

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Strings 67 of a string constant. It’s much more common to see both of these statements written on a single line by nesting one message send inside of another: NSString *myString = [[NSString alloc] initWithString:@"Hello, World!"]; As an alternative to the alloc- and init-based object creation process, most classes also provide factory methods that allow you to perform both steps at the same time. The following snippet shows another way to create a new string: NSString *myString = [NSString stringWithString:@"Hello, World!"]; This statement is identical in behavior to calling alloc, followed by initWithString:, but it’s slightly easier to read and quicker to type. In general, many initialization messages named in the form initWithXYZ: have a matching classnameWithXYZ: factory method available that performs an implicit alloc behind the scenes. A subtle but important difference in memory management between the two techniques is discussed in depth in chapter 9. For now, let’s stick to using factory methods. Using your newfound knowledge of object construction techniques, you can look at some of the previous code samples in a new light. For example, in the current version of the Rental Manager application is the following line of source code: cell.detailTextLabel.text = [NSString stringWithFormat:@"Rents for $%0.2f per week", properties[indexPath.row].weeklyRentalPrice]; With your knowledge of message-naming conventions, you can see that this statement creates a new string by sending the NSString class the stringWithFormat: message. This message constructs a new string by interpreting an NSLog-style format string. Now that you know how to create new string objects, let’s look at how to work with them. 3.5.2 Extracting characters from strings Once you create a string object, you’re ready to interact with it by sending the object a message. Perhaps the simplest message you can send to a string is the length message, which returns the total number of characters in the string: int len = [myString length]; NSLog(@"'%@' contains %d characters", myString, len); Because a string is made up of a sequence of individual characters, another message that is useful is characterAtIndex:, which allows you to obtain the character at a particular index within a string: NSString *myString = @"Hello, World!"; unichar ch = [myString characterAtIndex:7]; NSLog(@"The 8th character in the string '%@' is '%C'", myString, ch); Notice that the characterAtIndex: message works in a fashion similar to the array indexing operator [], available for C-style arrays. If instead of a single character you want to obtain a particular range of characters within a string, you can use the substringWithRange: message, as demonstrated by the following listing.
68 CHAPTER 3 An introduction to objects Listing 3.1 Using substringWithRange: to obtain the last word in a string NSString *str1 = @"Hello, World!"; NSRange range; range.location = 7;
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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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Page 39 and 40: 16 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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Page 97 and 98: Storing data in collections This ch
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Page 120 and 121: Creating classes This chapter cover
Page 122 and 123: Declaring the interface of a class
Page 130 and 131: Providing an implementation for a c
Page 132 and 133: Declared properties 109 - (Property
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Page 136 and 137: Declared properties 113 Although @s
Page 138 and 139: Creating and destroying objects 115
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Creating and destroying objects 117
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Creating and destroying objects 119
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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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Objective-C Fundamentals

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