The Objective-C Programming Language

Inside Mac OS X

The Objective-C Programming Language

February 2003

 Apple Computer, Inc.

? 2002 Apple Computer, Inc. All rights reserved.

No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, mechanical, electronic, photocopying, recording, or otherwise, without prior written permission of Apple Computer, Inc., with the following exceptions: Any person is hereby authorized to store documentation on a single computer for personal use only and to print copies of documentation for personal use provided that the documentation contains Apple's copyright notice.

The Apple logo is a trademark of Apple Computer, Inc. Use of the "keyboard" Apple logo (Option-Shift-K) for commercial purposes without the prior written consent of Apple may constitute trademark infringement and unfair competition in violation of federal and state laws.

No licenses, express or implied, are granted with respect to any of the technology described in this book. Apple retains all intellectual property rights associated with the technology described in this book. This book is intended to assist application developers to develop applications 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.

Even though Apple has reviewed this manual, APPLE MAKES NO WARRANTY OR REPRESENTATION, EITHER EXPRESS OR IMPLIED, WITH RESPECT TO THIS MANUAL, ITS QUALITY, ACCURACY, MERCHANTABILITY, OR FITNESS FOR A PARTICULAR PURPOSE. AS A RESULT, THIS MANUAL IS SOLD "AS IS," AND YOU, THE PURCHASER, ARE ASSUMING THE ENTIRE RISK AS TO ITS QUALITY AND ACCURACY.

IN NO EVENT WILL APPLE BE LIABLE FOR DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES RESULTING FROM ANY DEFECT OR INACCURACY IN THIS MANUAL, even if advised of the possibility of such damages.

THE WARRANTY AND REMEDIES SET FORTH ABOVE ARE EXCLUSIVE AND IN LIEU OF ALL OTHERS, ORAL OR WRITTEN, EXPRESS OR IMPLIED. No Apple dealer, agent, or employee is authorized to make any modification, extension, or addition to this warranty.

Some states do not allow the exclusion or limitation of implied warranties or liability for incidental or consequential damages, so the above limitation or exclusion may not apply to you. This warranty gives you specific legal rights, and you may also have other rights which vary from state to state.

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

CONTENTS

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

CONTENTS

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

 ................
................

In order to avoid copyright disputes, this page is only a partial summary.

Google Online Preview   Download