Introduction

Object-oriented programming, like most interesting developments, builds on some old ideas, extends them, and puts them together in novel ways. The result is many-faceted and a clear step forward for the art of programming. An object-oriented approach makes programs more intuitive to design, faster to develop, more amenable to modifications, and easier to understand. It leads not only to alternative ways of constructing programs, but also to alternative ways of conceiving the programming task.

Nevertheless, object-oriented programming presents some formidable obstacles to those who would like to understand what it's all about or begin trying it out. It introduces a new way of doing things that may seem strange at first, and it comes with an extensive terminology that can take some getting used to. The terminology will help in the end, but it's not always easy to learn. It can be difficult to get started.

That's where this book comes in. It's designed to help you become familiar with object-oriented programming and get over the hurdle its terminology presents. It spells out some of the implications of object-oriented design and tries to give you a flavor of what writing an object-oriented program is really like. It fully documents the Objective-C language, an object-oriented programming language based on standard C, and introduces the most extensive object-oriented development environment currently available-Cocoa.

The book is intended for readers who might be interested in:

Learning about object-oriented programming,
Finding out about the Cocoa development environment, or
Programming in Objective-C.

Apple supplies its own compiler for the Objective-C language (a modification of the GNU C compiler) and a run-time system to carry out the dynamic functions of the language. It has tested and made steady improvements to both over the years; this book describes the these improvements, which include provisions for declaring and adopting protocols and setting the scope of instance variables.

Throughout this book and in other Apple documentation, the term "Objective-C" refers to the language as implemented for the Cocoa development environment and presented here.