Changes

In previous chapters of ]][[Objective-C 2.0 Essentials]] we have covered the concept of object-oriented programming in considerable detail. So far, however, we have focused almost exclusively on the how to create and work with our own classes and objects within Objective-C programs.

Now that we have a firm understanding of how to work with objects we can now apply what we have learned to using a set of pre-existing classes that are provided with Objective-C to make our jobs as programmers much easier. These classes belong to the ''Foundation Framework''.

The Objective-C Foundation Framework is a essentially a set of classes that are provided to speed and ease the process of developing applications using Objective-C. The framework was developed by NeXT Computer as part of the NeXTStep environment. When NeXT was acquired by Apple, Inc. the Foundation classes quickly became of basis of Mac OS X and then the iPhone development kit. For a full history of how this came to be, refer to the chapter entitled [[The History of Objective-C]].

You will recall that when we created our first class in [[An Overview of Objective-C Object Oriented Programming]] we derived our class from ''NSObject''. NSObject is a part of the Foundation Framework and as you become more familiar with the framework you will learn that most Foundation classes are derived from this class). In this and subsequent chapters we will look in more detail at some of the other classes provided by the framework.

A detailed overview of every class and method in the Foundation Framework is beyond the scope of this book and would be largely redundant given that this information is already provided by Apple in various locations. Instead, this book will focus on teaching you how to use the most common Foundation classes to work with numbers, strings , arrays and file systems. This knowledge, combined with the Apple Foundation documentation should be all you need to be begin working proficiently with these classes.