In the recent 19 Rails Tricks Most Rails Coders Don't Know article, I recommended the use and development of engines to implement common functionality in Rails applications. I simply provided a link to the Rails Engines site and left it at that.
Active Merchant is a payment processing library for Rails developed by the geniuses behind Rails powered e-commerce system, Shopify. It's under active development with support for different payment processor gateways being added regularly. So far it supports:
There are many scenarios where you might want the same controller action / method in your Rails application to perform multiple functions. For example, a wizard with multiple steps or a single form with multiple-stage AJAX calls. What you want to do is provide a 'context' to the specific request and have the controller handle that in some different way.
The indefatigable Assaf Arkin has done it again by developing a new Ruby HTML scraping toolkit, scrAPI. Peter Szinek recently wrote a popular article about scraping from Ruby using Manic Miner, RubyfulSoup, REXML, and WWW::Mechanize, but none of these are as immediately useful as scrAPI.. so why?
This library is so amazingly cool that it requires no descriptions beyond these code examples:
Geoffrey Grosenbach introduces the RaPT Plugin Manager for Rails, the answer to the problem of slow plugin installation. Installable as a gem (gem install rapt), RaPT caches the locations of different plugins so that installation is quick and easy. Future plans include developing a central plugin repository, auto-announcement of self-developed plugins, and automatic plugin upgrading. If you want the files direct, check out the Rubyforge project site for RaPT.
You can test your controllers, your models, and, well, most of your application, but till now there hasn't been a way to explicitly test your Rails application's helpers. Now there's a solution.. the helper_test plugin (with source and instructions).
MeantimeFilter is an interesting new plugin for Rails by Roman Le Negrate. It's a little like around_filter, but rather than using a class with 'before' and 'after' methods, it uses a single method (like the other types of filter) and passes in the method to wrap 'around' as a code block. You can then yield to this or pass it into anything you like. An example:
Paul Battley has developed a Ruby to JavaScript converter. I'm trying to think what this is useful for, but this is an amazing results for just a few hours' work.