"I have a mind like a steel... uh... thingy." Patrick Logan's weblog.

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Sunday, August 21, 2011

On Cappuccino and Avoiding The Modern "Impedance" Mismatch

Wow. My head is just not geared toward writing a blog any longer. But I will model through it.

Cappuccino is a great system for writing rich web applications in the browser, without plugins. There's finally a growing emphasis on Model/View/Controller among modern javascript libraries. Most of them rely on HTML and CSS for the View mechanisms. Which is as you would expect. The problem is the "impedance mismatch" (if you will) between these mechanisms and the desired views for traditional rich applications.

Cappuccino does not suffer such a mismatch, being based on a good portion of the API of NeXTStep, OpenStep, GNUStep, and Apple's Cocoa. And so the Cappuccino API is essentially 25 years old or so.

This choice is not without its pro's and con's. The pro's win for me for applications with these characteristics:

  • At least one display screen greater than 10 inches, i.e. typically used on more than a tablet or phone
  • A good bit more data than would easily fit on a single page, and complex relationships throughout
  • More than a few operations on that data, with a good bit of keyboard input

Because Cappuccino provides an HTML view, this is not a total loss. I've not done much with this yet, but the "con" seems to become a "pro" by allowing for applying HTML and CSS when those mechanisms are the best fit.

Another initial "con" for me the first time I poked at Cappuccino turned "pro" eventually. I'd done a fairly extensive search several months ago on the state of the art of MVC for javascript. Cappuccino was low on my list because I wanted to use javascript per se. Just as Cocoa, et al. are written in Objective-C, Cappuccino is in Objective-J.

I actually like the syntax and class mechanisms, and their similarity to Objective-C and Smalltalk. (Also emacs' Objective-C mode works pretty well as-is with Objective-J.) As the javascript runtimes and tools are adapted to support multiple languages, the tool support for Objective-J should increase.

I came back to Cappuccino after frustration with manipulating HTML and CSS to do my bidding. I don't have any great need for the kind of styling afforded by HTML and CSS. (And with the fallback to an HTML view as per above, even less so.) Most of what I need can be provided satisfactorily using the traditional GUI views going back to Smalltalk-80's MVC.

As it happens, I've done a lot of GUI programming in Smalltalk and several other languages and libraries over the years, so my claim of the pragmatism of this approach also coincides with my experience. Some readers may recall a few years ago that I was in favor of programming web clients using Adobe Flex with ReSTful web services rather than immature javascript/HTML/CSS libraries.

The programmability of views from javascript/HTML/CSS is significantly better now than in 2007. But the majority of libraries are still immature and incomplete. Cappuccino is the best exception to the rule I know of. Fortunately one no longer requires a plugin to achieve Flex's level of productivity.

Cappuccino's class documentation is good, because the API and documentation is already 25 years mature. Tutorials and examples are good, growing, and fortunately supplemented by Cocoa material when the Capp material iteself is lacking.

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About Me

Portland, Oregon, United States
I'm usually writing from my favorite location on the planet, the pacific northwest of the u.s. I write for myself only and unless otherwise specified my posts here should not be taken as representing an official position of my employer. Contact me at my gee mail account, username patrickdlogan.