Afterword
Now that you have learned how to write Objective-C programs and use the Foundation framework, it's time to start writing your own Objective-C applications. You can use Appendix B, “Objective-C Language Summary,” to refresh your memory on the semantics of the language and for quick reference. You are also now well-prepared to read the “official” reference manual on Objective-C published by Apple Computer, Inc. It's listed in Appendix E, “Resources,” and is available online for free. Some more advanced topics (such as distributed objects) are covered in detail in that text.
As you've seen, the Foundation framework provides a solid foundation for program development, so take advantage of its many classes and learn how to use them to your advantage. Skim through the header file descriptions in Appendix B and see whether you find anything intriguing.
Some features offered by the Foundation framework were not covered in the text, either due to their advanced nature or lack of space. These include ways to
• Register an object to be notified when a particular event on the system occurs. This is handled primarily by Foundation's NSNotification class.
• Communicate with objects in different processes on the same system or on different systems. This is handled primarily by Foundation's NSConnection class.
• Work with dates with Foundation's NSDate and NSCalendarDate classes.
• Work with rectangles, sizes, and Cartesian coordinates using the defined types NSRect, NSSize, and NSPoint, respectively.
• Set up a run loop to process input events using the NSRunLoop class. (You'll want to learn how to do that for developing interactive graphical applications, multithreaded programs, or network I/O.)
• Set up a way to handle exceptions (that is, errors that occur in a running application). This is handled with Foundation's NSException class.
• Work with URLs to load and unload data, manage cookies, and so on. These are handled primarily through the NSURL, NSURLHandle, and NSHTTPCookie classes in Foundation.
• Write multithreaded applications. Multithreaded applications can be used to have one or more portions of an application executed in parallel to the rest of the application. The NSThread and NSLock classes (and several other classes) in Foundation are used to develop multithreaded Objective-C programs.
Refer to the resources in Appendix E for more information on these topics.
If you want to start writing applications using a graphical user interface (GUI), you should learn how to use the Application Kit framework, which is part of Cocoa on Mac OS X. Appendix E lists books you can read to gain this knowledge. On Mac OS X, you also should learn how to use the tools that will make your development time more productive, such as Project Builder (or Xcode if it's available on your system) and Interface Builder. GNUStep also offers a variety of development tools, as well as a GUI library, which you might want to learn how to use.
Good luck in your programming efforts!
Stephen Kochan[email protected]