Volume Number: 19 (2003)
Issue Number: 7
Column Tag: Reviews
by Ron Davis
I have to confess that I worked with Joe Zobkiw on my first job out of college working on Virex almost ten years ago. I was one of the tech reviewers for his previous book A Fragment of Your Imagination, which covered the esoteric programming arts of init, cdev, and other code fragments. It was one of those books that covered stuff no other book covered, the really low level crap most of us attempt to avoid. At the time there was next to no documentation on coding these things and Zobkiw's book was written to meet that need.
Mac OS X Advanced Development Techniques (MADT) is like that book. Not that it talks about the stuff you are trying to avoid writing, but it is talking about the things no one else is. There isn't as much low level stuff you can mess with in OSX, but there are a lot of little nooks and crannies of code that need explanations. Need to write a System Preference panel? It's there. How about adding one of those system-wide menus? Got you covered. They're called Status Items, Chapter 9. Screen saver? Chapter 10.
It also covers some less stand-alone stuff, like threads, frameworks and how to talk between a Cocoa app and a command-line tool. There is also a good chapter of "snippets", little pieces of code you often want, but that don't merit a long discussion.
In my opinion, this book is really aimed at the experienced OSX developer. The introduction says anyone who can compile a program in Project Builder can use it. I think you probably need a little more experience than that. I was interested in the book as a follow up to the various OSX development books I already had. If you have no understanding of Cocoa and want to write a screensaver, this book may not be the place to start.
Given the level of experience required for the book, I thought the first chapter was a waste of time. It is a very high level overview of MacOS in general and MacOS development. Most people already know about Quartz, Project Builder, FreeBSD.
The second chapter at first looked like more of the same, but I found the brief descriptions of the all of the developer applications helpful, if a little shallow. Especially interesting was the listing of command line tools useful to the developer.
Another general thing about the book. Zobkiw is a long time developer of Mac software and this book is plainly written assuming you are coming from a Mac background. If you're a Windows user or a UNIX guy, some stuff might go right by you, but none of it is really critical.
The first chapter with code in it is a document-based Cocoa app. This isn't a simple text edit style doc app either, but an app that watches Doppler radar pictures on the web and alerts you when a color in them change. I like that. I don't need another simple simple application, I want something that shows me a lot while it teaches the basics of a document based app.
The book also doesn't go through creation of the project step by step, but assumes you downloaded the project and just need it explained to you. This is appropriate for an advanced audience.
The only problem I had with the app was the document class uses readFromFile:ofType: and writeToFile:ofType instead of dataRepresentationOfType: and loadDataRepresentation:ofType which are what the standard document template creates for you. Nor does he mention these other routines and explain why one would be better or worse than the other.
The next two chapters discuss plug-ins, both Carbon and Cocoa. It is a very useful overview and explanation of how the various plug-in architectures work in OSX.
The last chapter in this section covers Frameworks, showing how to build both a Carbon and Cocoa version of a simple Framework.
The second section of the book was advanced topics for the application writer. The third section covers how to build unusual non-applications. Specifically System Services, System Preference Panes, Status Items (system-wide menus), Screen Effects (screen savers), and Color pickers.
You've probably noticed the Services sub-menu of a lot of apps. Under 10.1 this was a dead give away you were using a Cocoa, but 10.2 made them available to Carbon apps as well. They are programs, normally faceless, that interact with the current selection. Zobkiw explains how to write one of these services, creating an example that changes the case of the selected text.
Next Zobkiw talks about how to write a System Preference panel. This allows you to provide a basic UI for faceless application that run all of the time. The example in this chapter sets the preference for the Service created in the previous chapter.
Zobkiw gives an informative discussion of the various kinds of little menus that are displayed in the menu bar on the right side. Some of these are Status Items, some of them Menu Extras. Technically, we developers are only allowed to create Status Items; Menu Extras are reserved for Apple. The example in this chapter is of a Status Item and not a Menu Extra.
I was always a little jealous of how Windows has a standard screen saver mechanism and OS9 didn't. Well that changed in OSX and now you can very easily write those screen savers yourself. They're so easy the chapter explaining them is only 7 pages long. It is still a good introduction that leaves you with a place to start writing your own. If you are going to do a lot of Screen Effects work, you will want to get Saver Lab (http://www.dozingcat.com/), which allows you to run your screen saver in a window for debugging.
The last esoteric piece of code in this section is a Color Picker. The OSX Color Picker is actually a collection of pickers. When you open it there is a list of icon buttons at the top of the window that let you pick from a number of pickers. Third party developers can create their own picker panels using Cocoa. Chapter 11 gives you the details on how to do this.
Threads is the first of the advanced topics discussed, which gives you an overview of what threads are and how they work, and gives you an example of how to use them.
Terminal is the name of the next chapter, but it is really about NSTask and another thread example. Of all the chapters, this was the one I liked the least, because I felt it didn't really cover the topic and was just kind of wrong. He tells you how to use an NSTask to launch a UNIX command line command, but when he does one that you have to wait to return, he uses a thread that polls for the result. It really should have used the notifications NSTask has built into it. That is the right way to do it and the code would have been simpler.
The last two topics covered by their own chapters were XML-RPC and SOAP. These chapters give a basic introduction to using WebServices both in PHP and Cocoa. The PHP for the server made sense, though I was a little surprised Zobkiw did a PHP client. He also builds a client in Cocoa using the WebServices API in CoreServices. These two chapters are very similar. If you have a preference for one remote procedure call methodology over the other, you probably only need to read one of these chapters.
The last chapter of the book is a collection of snippets. Bits and pieces of code that you will find useful, but don't rate a full chapter. This may be the section you find most useful.
Overall I would say this book is a must have for a complete Cocoa bookshelf. It covers topics no other book covers and does it in a concise, referenceable way.
Ron Davis is a long time Macintosh Software Engineer, having worked for companies like Apple, and Metrowerks on a variety of products from development tools to anti-virus software. His day job is working for Alsoft, and his evening job is R.A.D. Productions, makers of Suck It Down and FinderEye.
