The Objective-C Programming Language - Andrew T. Duchowski

240 Pages·2003·2.62 MB·English

I n s i d e M a c O S X
The Objective-C Programming
Language
February 2003
 Apple Computer, Inc. Even though Apple has reviewed this
© 2002 Apple Computer, Inc. manual, APPLE MAKES NO
All rights reserved. WARRANTY OR REPRESENTATION,
EITHER EXPRESS OR IMPLIED, WITH
No part of this publication may be
RESPECT TO THIS MANUAL, ITS
reproduced, stored in a retrieval
QUALITY, ACCURACY,
system, or transmitted, in any form or
MERCHANTABILITY, OR FITNESS
by any means, mechanical, electronic,
FOR A PARTICULAR PURPOSE. AS A
photocopying, recording, or
RESULT, THIS MANUAL IS SOLD “AS
otherwise, without prior written
IS,” AND YOU, THE PURCHASER, ARE
permission of Apple Computer, Inc.,
ASSUMING THE ENTIRE RISK AS TO
with the following exceptions: Any
ITS QUALITY AND ACCURACY.
person is hereby authorized to store
documentation on a single computer IN NO EVENT WILL APPLE BE LIABLE
for personal use only and to print FOR DIRECT, INDIRECT, SPECIAL,
copies of documentation for personal INCIDENTAL, OR CONSEQUENTIAL
use provided that the documentation DAMAGES RESULTING FROM ANY
contains Apple’s copyright notice. DEFECT OR INACCURACY IN THIS
The Apple logo is a trademark of MANUAL, even if advised of the
Apple Computer, Inc. possibility of such damages.
Use of the “keyboard” Apple logo THE WARRANTY AND REMEDIES SET
(Option-Shift-K) for commercial FORTH ABOVE ARE EXCLUSIVE AND
purposes without the prior written IN LIEU OF ALL OTHERS, ORAL OR
consent of Apple may constitute WRITTEN, EXPRESS OR IMPLIED. No
trademark infringement and unfair Apple dealer, agent, or employee is
competition in violation of federal authorized to make any modification,
and state laws. extension, or addition to this warranty.
No licenses, express or implied, are
Some states do not allow the exclusion or
granted with respect to any of the
limitation of implied warranties or
technology described in this book.
liability for incidental or consequential
Apple retains all intellectual property
damages, so the above limitation or
rights associated with the technology
exclusion may not apply to you. This
described in this book. This book is
warranty gives you specific legal rights,
intended to assist application
and you may also have other rights which
developers to develop applications
vary from state to state.
only for Apple-labeled or
Apple-licensed computers.
Every effort has been made to ensure
that the information in this document
is accurate. Apple is not responsible
for typographical errors.
Apple Computer, Inc.
1 Infinite Loop
Cupertino, CA 95014
408-996-1010
Apple, the Apple logo, and
Macintosh are trademarks of Apple
Computer, Inc., registered in the
United States and other countries.
HotSpot is a trademark of Sun
Microsystems, Inc.
Simultaneously published in the
United States and Canada.
Contents
Figures, Listings, and Tables 11
Chapter 1 Introduction
The Development Environment 14
Why Objective-C 15
How This Book is Organized 16
Conventions 17
Chapter 2 Object-Oriented Programming
Interface and Implementation 20
The Object Model 24
The Messaging Metaphor 26
Classes 28
Modularity 29
Reusability 30
Mechanisms Of Abstraction 31
Encapsulation 32
Polymorphism 33
Inheritance 35
Class Hierarchies 35
Subclass Definitions 36
Uses of Inheritance 37
Dynamism 39
Dynamic Typing 39
Dynamic Binding 40
Dynamic Loading 43
Structuring Programs 44
Outlet Connections 45
3
 Apple Computer, Inc. February 2003
C O N T E N T S
Extrinsic and Intrinsic Connections 47
Activating the Object Network 47
Aggregation and Decomposition 48
Models and Frameworks 49
Structuring the Programming Task 50
Collaboration 51
Organizing Object-Oriented Projects 52
Designing on a Large Scale 52
Separating the Interface from the Implementation 52
Modularizing the Work 52
Keeping the Interface Simple 53
Making Decisions Dynamically 53
Inheriting Generic Code 53
Reusing Tested Code 54
Chapter 3 The Objective-C Language
Objective-C Objects 55
id 56
Dynamic Typing 57
Object Messaging 58
The Receiver’s Instance Variables 59
Polymorphism 60
Dynamic Binding 60
Classes 62
Inheritance 62
The NSObject Class 64
Inheriting Instance Variables 64
Inheriting Methods 65
Overriding One Method With Another 66
Abstract Classes 66
Class Types 67
Static Typing 67
Type Introspection 68
Class Objects 68
Creating Instances 70
Customization With Class Objects 71
4
 Apple Computer, Inc. February 2003
C O N T E N T S
Variables and Class Objects 72
Initializing a Class Object 73
Methods of the Root Class 74
Class Names in Source Code 74
Defining a Class 75
The Interface 76
Importing the Interface 78
Referring to Other Classes 79
The Role of the Interface 79
The Implementation 80
Referring to Instance Variables 82
The Scope of Instance Variables 83
How Messaging Works 87
Selectors 90
Methods and Selectors 91
Method Return and Argument Types 91
Varying the Message at Runtime 92
The Target-Action Paradigm 92
Avoiding Messaging Errors 94
Hidden Arguments 94
Messages to self and super 95
An Example 96
Using super 99
Redefining self 99
Extending Classes 101
Categories—Adding Methods to Existing Classes 101
Adding to a Class 102
How Categories Are Used 103
Categories of the Root Class 103
Protocols—Declaring Interfaces for Others to Implement 104
When to Use Protocols 105
Enabling Static Behaviors 115
Static Typing 116
Type Checking 117
Return and Argument Types 118
Static Typing to an Inherited Class 118
Getting a Method Address 120
Getting an Object Data Structure 120
5
 Apple Computer, Inc. February 2003
C O N T E N T S
Using C++ With Objective-C 122
Mixing Objective-C and C++ Language Features 122
C++ Lexical Ambiguities and Conflicts 125
Chapter 4 The Objective-C Runtime System
Memory Management 129
Allocating and Initializing Objects 129
The Returned Object 130
Arguments 131
Coordinating Classes 132
The Designated Initializer 134
Combining Allocation and Initialization 139
Retaining Objects 140
Handling Cyclical References 141
Deallocation 142
Releasing Shared Objects 143
Releasing Instance Variables 144
Marking Objects for Later Release 144
Object Ownership 145
Forwarding 146
Forwarding and Multiple Inheritance 149
Surrogate Objects 150
Forwarding and Inheritance 150
Dynamic Loading 152
Remote Messaging 152
Distributed Objects 153
Language Support 155
Synchronous and Asynchronous Messages 156
Pointer Arguments 157
Proxies and Copies 159
Type Encodings 160
Chapter 5 Objective-C Runtime Functions and Data Structures
Objective-C Functions 165
6
 Apple Computer, Inc. February 2003
C O N T E N T S
Accessing Selectors 166
sel_getName 166
sel_isMapped 167
sel_registerName 167
sel_getUid 168
Sending Messages 168
objc_msgSend 169
objc_msgSend_stret 169
objc_msgSendSuper 170
objc_msgSendSuper_stret 171
Forwarding Messages 172
objc_msgSendv 172
objc_msgSendv_stret 173
marg_malloc 173
marg_free 174
marg_getRef 174
marg_getValue 174
marg_setValue 175
Adding Classes 175
objc_addClass 175
Accessing Methods 178
class_getInstanceMethod 178
class_getClassMethod 179
class_nextMethodList 179
class_addMethods 180
class_removeMethods 181
method_getNumberOfArguments 182
method_getSizeOfArguments 182
method_getArgumentInfo 182
Accessing Instance Variable Definitions 183
class_getInstanceVariable 183
Accessing the Class Version 183
class_setVersion 183
class_getVersion 184
Posing As Another Class 185
class_poseAs 185
Obtaining Class Definitions 185
objc_getClassList 186
7
 Apple Computer, Inc. February 2003
C O N T E N T S
objc_getClass 187
objc_lookUpClass 188
objc_getMetaClass 188
objc_setClassHandler 189
Instantiating Classes 189
class_createInstance 189
class_createInstanceFromZone 190
Accessing Instance Variables 190
object_setInstanceVariable 191
object_getInstanceVariable 191
Objective-C Callbacks 192
Class Handler Callback 192
Objective-C Data Types 192
Class Definition Data Structures 193
objc_class 194
objc_ivar 196
objc_ivar_list 197
objc_method 198
objc_method_list 199
objc_cache 200
objc_protocol_list 201
Instance Data Types 201
objc_object 202
objc_super 202
Appendix A Objective-C Language Summary
Messages 205
Defined Types 206
Preprocessor Directives 207
Compiler Directives 207
Classes 208
Categories 209
Formal Protocols 210
Method Declarations 211
Method Implementations 212
Naming Conventions 212
8
 Apple Computer, Inc. February 2003
C O N T E N T S
Appendix B Grammar for the Objective-C Language
External Declarations 217
Type Specifiers 221
Type Qualifiers 222
Primary Expressions 222
Chapter C Document Revision History
Glossary 227
Index 233
9
 Apple Computer, Inc. February 2003
C O N T E N T S
10
 Apple Computer, Inc. February 2003