Notes from Ruby SIG, 16-Aug-2010

The New Hampshire Ruby/Rails group met as usual on the 3rd Monday of the month. We met at the New Hampshire Innovation Commercialization Center, a new space near the Pease airfield. Mark Galvin, NHICC’s Managing Director, was kind enough to offer the space for our meeting and tell us about the ICC. Eleven members attended the meeting.

As we often do, we started with a round of introductions. It’s always interesting to find out who’s there and what they’re up to. I mentioned the GNHLUG calendar and Nick plugged the upcoming Rails Rumble. Near the end of the meeting, we plugged the NorthEast RailsCamp, coming up on it’s third meeting, this one in Stowe, VT. 5 alums from previous camps were there, and all loved it. There may still be a ticket or two left, even though the site says zero – you’d better hurry!

We were lucky enough to have two presentations tonight.

Brian Turnbull presented “Interfacing Ruby with C.” He explained he needed to do some automation with a “black box” his company was using, and their documentation consisted of a C API and a DLL. Rather than developing an entire application in C, he used Ruby to interface to the C API and then could develop an easy-to-modify Ruby app. That turned out to be a good idea, as the final product he delivered turned out to be very different from the initial request, and having the ability to rapidly re-develop in Ruby was a success. To show us how to use C to access Ruby and vice-versa, Brian used a simple example of a “leaky bucket stack,” a fixed-length stack that would lose the oldest item as the stack was pushed. It was a great example in that it had enough complex behavior to be useful, while simple enough to explain and translate into C without too much effort. First, we reviewed the pure Ruby implementation. Brian proceeded to build up the equivalent code in C, calling Ruby array functionality and data types where appropriate. He then showed how to configure the C extension from from Ruby, build, compile, debug and run from the ruby command line.

See the example code and slides (I’ll update the URL when available). Also http://github.com/bturnbull/padpaws for his more advanced C example.

Brian Cardarella, @bcardarella, http://bcardarella.com, presented his gem, client-side validation, which he developed while working on the “Raise Your Vote” site for the Democratic National Committee. The Raise Your Vote site is intended to assist in voter registration by collecting data online and generating matching PDFs of the voter application. Naturally, 50 states have fifty different forms, with different requirements. He wanted to avoid duplicating the server-side validations with hand-maintained client side code, as the regular changing of requirements and the difficulty of keeping business rules in synch across the two languages would doom the project. He wrote client-cisde_validations to use the declarative validations within the entity models to generate the equivalent Javascript code. Client-side_validations has remarkable depth and breadth, handling nearly all of the common and exceptional types of valiation (Brian notes the few difficult cases in his slides). You can find the code on GitHub (gem code, examples) and the slides here: client_side_validations.pdf

Thanks to Brian Cardarella for travelling all the way to Portsmouth and thanks to both Brians for their fine presentations. Thanks to Nick Plante and Brian Turnbull for organizing and promoting the meeting and the group. And thanks to Mark Galvin and the New Hampshire Innovation Commercialization Center for providing the fine facilities!

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