The Objective-C language is a simple computer language designed to enable sophisticated object-oriented programming. Objective-C is defined as a small but powerful set of extensions to the standard ANSI C language. Its additions to C are mostly based on Smalltalk, one of the first object-oriented programming languages. Objective-C is designed to give C full object-oriented programming capabilities, and to do so in a simple and straightforward way.

Most object-oriented development environments consist of several parts:

• An object-oriented programming language
• A library of objects
• A suite of development tools
• A runtime environment

This document is about the first component of the development environment—the programming language. It fully describes the Objective-C language, and provides a foundation for learning about the second component, the Mac OS X Objective-C application frameworks—collectively known as Cocoa. You can start to learn more about Cocoa by reading Getting Started with Cocoa. The two main development tools you use are Xcode and Interface Builder, described in Xcode Workspace Guide and Interface Builder respectively. The runtime environment is described in a separate document, Objective-C 2.0 Runtime Programming Guide.

Contents
Introduction Introduction to The Objective-C 2.0 Programming Language

Who Should Read This Document
Organization of This Document
Conventions
See Also
Runtime
Memory Management

Chapter 1 Objects, Classes, and Messaging

Runtime
Objects
Object Basics
id
Dynamic Typing
Memory Management

Object Messaging

Message Syntax
Sending Messages to nil
The Receiver’s Instance Variables
Polymorphism
Dynamic Binding
Dynamic Method Resolution
Dot Syntax

Classes

Inheritance
Class Types
Class Objects
Class Names in Source Code
Testing Class Equality

Chapter 2 Defining a Class

Source Files
Class Interface
Importing the Interface
Referring to Other Classes
The Role of the Interface

Class Implementation

Referring to Instance Variables
The Scope of Instance Variables

Messages to self and super


An Example
Using super
Redefining self

Chapter 3 Allocating and Initializing Objects

Allocating and Initializing Objects
The Returned Object
Implementing an Initializer
Constraints and Conventions
Handling Initialization Failure
Coordinating Classes

The Designated Initializer
Combining Allocation and Initialization

Chapter 4 Declared Properties

Overview
Property Declaration and Implementation
Property Declaration
Property Declaration Attributes
Property Implementation Directives

Using Properties

Supported Types
Property Re-declaration
Copy
dealloc
Core Foundation
Example

Subclassing with Properties
Performance and Threading
Runtime Difference

Chapter 5 Categories and Extensions

Adding Methods to Classes
How you Use Categories
Categories of the Root Class
Extensions

Chapter 6 Protocols

Declaring Interfaces for Others to Implement
Methods for Others to Implement
Declaring Interfaces for Anonymous Objects
Non-Hierarchical Similarities
Formal Protocols
Declaring a Protocol
Optional Protocol Methods

Informal Protocols
Protocol Objects
Adopting a Protocol
Conforming to a Protocol
Type Checking
Protocols Within Protocols
Referring to Other Protocols

Chapter 7

Fast Enumeration
The for…in Feature
Adopting Fast Enumeration
Using Fast Enumeration

Chapter 8 Enabling Static Behavior

Default Dynamic Behavior
Static Typing
Type Checking
Return and Argument Types
Static Typing to an Inherited Class

Chapter 9 Selectors

Methods and Selectors
SEL and @selector
Methods and Selectors
Method Return and Argument Types

Varying the Message at Runtime
The Target-Action Design Pattern
Avoiding Messaging Errors

Chapter 10 Exception Handling

Enabling Exception-Handling
Exception Handling
Catching Different Types of Exception
Throwing Exceptions

Chapter 11 Threading

Synchronizing Thread Execution

Chapter 12 Remote Messaging
Distributed Objects
Language Support

Synchronous and Asynchronous Messages
Pointer Arguments
Proxies and Copies

Chapter 13 Using C++ With Objective-C

Mixing Objective-C and C++ Language Features
C++ Lexical Ambiguities and Conflicts
Limitations
Appendix A
Language Summary
Messages
Defined Types
Preprocessor Directives
Compiler Directives
Classes
Categories
Formal Protocols
Method Declarations
Method Implementations
Deprecation Syntax
Naming Conventions

Glossary
Document Revision History
Index

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