Mar 99 Online
Volume Number: 15
Issue Number: 3
Column Tag: MacTech Online
by Jeff Clites <online@mactech.com>
Make your applications scriptable.
The advice is as simple as that.
The standard reasoning is that by making your application AppleEvent-aware, you
make it move valuable - users can automate repetitive tasks and incorporate your
product into a larger workflow. Recently I was reading the FAQ for the popular FTP
client Anarchie Pro (by Stairways Software). The question on the table was, "Why
don't you give Anarchie the ability to repeatedly poll busy FTP sites until it can get
in?" The answer was that they don't want to add this feature, because it would be a
disservice to the already-busy FTP sites, but you can achieve the same effect using
AppleScript. I found this intriguing - not only does scriptability save the authors from
having to program in this functionality themselves, but also it allows them to
discourage using their product this way, but still allows the user to make the final
decision on the matter. That is the gem of scriptability - empowering your users to
use your product in ways that you didn't predict.
There's a second, more subtle motivation to making your applications AE-aware - it
makes your design better. If you want to make your application extensively scriptable
(and recordable), you need to factor it correctly - to separate the UI from the
implementation as much as possible. One method for doing this is the
Model-View-Controller paradigm, which incidentally is the way most Yellow Box
applications are developed. So there's a nice harmony here - factoring your
applications to make them scriptable also prepares you for later moving to Yellow Box
development, and Yellow Box development is by default done in a manner which makes
it trivial to add extensive scripting capabilities to applications.
There are three separate aspects of AppleEvents which might be important to you as a
programmer: making your application AppleEvent-aware (your application is an
AE-server), controlling other applications with AppleEvents (your application is an
AE-client), and writing applications in AppleScript itself. This month we are going to
point out some informational resources for each, and next month we'll look at some
utilities and libraries to help with the implementation.
Getting Started - General Resources for Developers
The definitive references of course come from Apple. The Interapplication
Communication (IAC) section of their Mac OS 8 Developer Documentation provides
pointers to the essential publications and technotes, including their AppleScript for
Developers page. Another key resource is articles from back-issues of Apple's
now-defunct journal develop. They have a page which collects links to all of the IAC
articles, and these are also all available in HTML form, complete with accompanying
source code, on MacTech's web site. A similar, annotated list is available on Main
Event's site. For a printed reference, I highly recommend Dave Mark's Ultimate Mac
Programming (ISBN 1-56884-195-7). Don't let its uninformative title fool you - about a third of this thick volume is devoted to getting the developer up to speed with
all things AppleEvent-related, and I have yet to find a reference which does a better
job of explaining the subject and getting you oriented.
Mac OS 8 Developer Documentation: Interapplication Communication
http://developer.apple.com/techpubs/macos8/InterproCom/interprocom.htm
l
Mac OS 8 Developer Documentation: AppleScript for Developers
http://developer.apple.com/techpubs/macos8/InterproCom/AppleScriptDev/
applescriptdev.html
develop Articles on Interapplication Communication
http://developer.apple.com/dev/techsupport/develop/bysubject/iac.html
develop in MacTech
http://www.mactech.com/articles/develop/
Main Event - Resources - Articles
http://www.mainevent.com/articles.tmpl
For a glimpse of the future, take a look at the Scripting documentation for Mac OS X
Server. Yellow Box applications will get a great deal of scriptability "for free", and it
will be easy to extend their scriptability further. Scripting fits nicely with the Yellow
Box application model, and promises to have a bright future under Mac OS X later this
year.
Mac OS X Server Developer Documentation
http://developer.apple.com/techpubs/macosxserver/macosxserver.html
Making Your Application AppleEvent-Savvy - Two Key
Articles
Included among the develop articles mentioned above are two that I think are key.
Ideally you would read all of them, but failing that check out "Programming for
Flexibility: The Open Scripting Architecture" which is foundational and really gives
you a feel for the power of Apple's scripting architecture, and "According to Script:
Attaching and Embedding Scripts" which I hope will sell you on the virtues of this
powerful but underutilized technique. (The simplest example is just providing your
users with a "scripts" menu.)
Architecture
http://www.mactech.com/articles/develop/issue_18/026-040_SMITH_REV
.html
June 96 - According to Script: Attaching and Embedding Scripts http://www.mactech.com/articles/develop/issue_26/according.html
Stay tuned for next month, when we'll cover development tools to make your
AppleEvent programming a breeze.
These and a bevy of other links are available from the MacTech Online web pages at
http://www.mactech.com/online/.