Learning Cocoa

Chapter 3. Objective-C Primer

The Objective-C language is a superset of ANSI C with special syntax and runtime extensions that make object-oriented programming possible. Objective-C syntax is uncomplicated, but powerful in its simplicity. You can mix standard C with Objective-C code. Programmers familiar with C and object-oriented programming techniques often find themselves right at home with Objective-C in a matter of days.

This chapter is divided into two main sections. The first section is a basic language summary listing all additions to the language. The second section summarizes some of the most frequently used aspects of the language.

See Inside Cocoa: Object-Oriented Programming and the Objective-C Language in /Developer/Documentation/Cocoa for complete details.

Language Summary

Objective-C adds a small number of constructs to the C language and defines a handful of conventions used to effectively interact with the runtime system.

Messages

Message expressions are enclosed in square brackets:

[receiver message]

The receiver can be:

• A variable or expression that evaluates to an object (including the variable self)

• A class name (indicating the class object)

• super (indicating an alternative search for the method implementation)

The message is the name of a method plus any arguments passed to it.

Defined Types

The principal types used in Objective-C are defined in the header file objc/objc.h:

Type	Definition
id	An object (a pointer to its data structure)
Class