Volume Number: 14 (1998)
Issue Number: 9
Column Tag: MacTech Online
by Jeff Clites, online@mactech.com
Code reuse was one of the key motivating forces behind the development of object-oriented programming. It's a simple idea, really - come up with a way to organize code so that conceptually separate pieces are independent and self-contained. Then, since these pieces don't rely on other parts of an application, they can be reused in multiple projects without modification.
The obvious next step in this evolution is the development of application frameworks, and the idea here is simple, too: most Macintosh applications, for instance, have a lot of code in common - they initialize managers, track mouse clicks in menus, and use scroll bars. This is where a framework comes in - it collects commonly-used code and organizes it so that you can develop an application by focusing on the parts which make your application distinctive while ignoring the mundane. This frees you from the burden of writing the same code over and over, and provides you with well-debugged code to do the dirty work. This all sounds great - so you may be asking, "what's the problem?"
Beginning C++ programmers on the Mac face a bit of a Catch-22. On the one hand, they need to be able to test out small stretches of code while they are learning, but there really is a lot of work to be done just to get a small application up and running. So, they could really benefit from a framework - it would relieve them from writing support code which they don't yet feel confident writing, and would allow them to be pretty sure that if something doesn't work then it is a problem with their code and not, say, that they forgot to initialize TextEdit. But, frameworks such as Apple's MacApp and Metrowerks' PowerPlant were not designed with the beginner in mind - they were designed for industrial-strength commercial application development. (For instance, the front end to the Mac version of Netscape Navigator is PowerPlant-based.) Despite excellent documentation, they can be overwhelming, especially for someone who is just learning what inheritance and polymorphism are all about.
This is where MacZoop comes in. It is a small (well, maybe medium-sized) Macintosh application framework generously developed and supported by Graham Cox, and it was specifically designed to be a learning tool for those just starting out with C++. And, in the spirit of enriching the Macintosh community, it's free.
In fact, without any additional code MacZoop builds into a working application. The application doesn't do much, but it has File and Edit menus with the usual menu items, and you can open new (empty) windows which are movable, zoomable, and resizable, and they tile nicely across the screen, just as you would expect from a Mac application. This may not sound like much, but any Mac programmer knows how much effort it takes to set up such things, and how hard it can be for a beginner. This lets them build their code in top of something which already works.
Graham has included a full bag of goodies to help you along. There is an electronic manual, just shy of 200 pages, which uses color more effectively than any other technical documentation I have seen. It provides a compact introduction to the key concept of C++ and of programming the Macintosh in general, and really touches on most subjects that a first-time Mac programmer needs to have under his belt. Also, there is a small demo application showing off many of its main features, and a full-featured paint program which serves as a more extensive example. (Both, of course, come with full source code, and the manual has detailed instructions for compiling the framework using CodeWarrior.)
MacZoop sports a wealth of very clever features which make it useful beyond its role as a learning tool, and it warrants a look from more experienced programmers as well. For example, if you create a window with one of the traditional floating-window WDEFs, it floats - it stays above all other windows in your application, and hides itself when your application goes into the background - you don't have to worry about the details. It also takes full advantage of ResEdit as an interface editor; for instance, it provides two separate methods (one based on TCL and one on MacApp) for associating commands with menu items, so that after setting up your resources you can forget about your menus and think in terms of commands that your classes understand. ResEdit is also used to create enhanced dialogs, with icon lists or scrolling text boxes installed as easily as any other control.
A few other niceties round out the package, and are worthy of special mention. The framework comes with its own small set of container classes and avoids any use of the STL. This seems to violate the spirit of code reuse, since it duplicates functionality already available as part of the language. But it is actually a clever move - it introduces the concept of containers and templates without requiring a full understanding of the ins and outs of the STL, and it avoids the code bloat often associated with it. Finally, there are many utility classes which make things like creating custom icons or displaying JPEGs a snap.
Well, I hope I've given you a sense of what MacZoop has to offer to beginners and to experts alike - there are a multitude of features that I didn't get to mention. In addition to the core distribution, there are a few must-have items contributed by other authors. M. Uli Kusterer has written an extensive set of pane classes specifically for MacZoop, which allow you to organize elements of your visual interface in a natural, hierarchical manner. Uli is also developing Resurrection, a free resource editor for use with MacZoop, written (of course) using MacZoop itself. Finally, Joe Strout has a smaller set of pane classes, which work with MacZoop and with his own framework Moof, which is much smaller than 'Zoop and which would also be well-suited to a beginner.
I encourage you to give MacZoop a look, or to point it out to your friends who are just beginning to tinker with programming on the Mac. Professional programmers will at some point want to learn about larger frameworks, but MacZoop will introduce you to concepts that you can take with you when you move on, and it's a rich source of code snippets and example of how to do things the "right" way. This is an especially exciting time to be a Mac developer, with the advent of Mac OS X and ever-faster hardware, and I hope that MacZoop and the work of other generous folk can help open the door to non-programmers wishing to try their hand. Graham intends to make MacZoop fully Mac OS X compliant as soon as the API is finalized (support for Appearance and Navigation Services is in place now), and he has already begun work on a gaming framework built around MacZoop. It should all be a lot of fun.
These and piles of other links are available from the MacTech Online web pages at www.mactech.com/online/.
