Appendix A. iPhone OS class reference
After this book, your main resource for learning more about the iPhone should be the references at developer.apple.com. To help you find documents that might interest you, this appendix lists the major classes in the UIKit and Foundation hierarchies that you might want to know more about, excluding classes that only appear as a part of another class.
The UIKit framework contains those classes most tightly connected to the iPhone, including all of the graphical classes you use to make up pages. A partial listing appears as table A.1. It’s current as of iPhone OS 2.1, and will probably be mostly correct when you read this, but the UIKit does sometimes change between releases.