Rails 3 is coming!
I've been doing a lot of thinking about how I can help clients get in a better position to upgrade to Rails 3 when it's ready for prime time. There's a few things you can do today with your 2.3.x application to give it more Rails 3 flava. Yeah boy!!!
Use Bundler instead of config.gem
Yehuda Katz has done a good job replacing config.gem with a more platform agnostic utility called Bundler. The API has changed around a bit with the latest 0.9 release, but he supplies a decent guide. For details on what's changed since that writeup, check out this post from Yehuda
Use inherited_resources to get respond_with
respond_with will be a nice shortcut in Rails 3 for the rendering end of RESTful controller actions. Jose Valim's inherited_resources actually gives you respond_with and respond_to methods for Rails 2.3.x applications. No more repetitive and un-DRY respond_to blocks
Unsafe strings will automatically be escaped by default in Rails 3. If you want this behavior in 2.3.x, all you have to do is install Koz's rails_xss. It is surprisingly hard to break out of the habit of using h() calls in your markup, though! Additionally, be wary that you might have to hack some of your view related plugins to get them working with rails_xss.
Use More Named Scopes
Fortunately, ActiveRecord find() calls will soon be unfound in Rails applications. Pratik has done some really cool stuff with active_record. These changes are all pretty significant, but perhaps the largest deal is that the find() method and its relatives will be deprecated come Rails 3.1. One thing that is remaining a fairly consistent part of the API is named_scopes (despite a name change).
Developers should be encouraged to use named_scopes and association chains even more aggressively, now. It will certainly be easier to refactor a few named scopes around than it would be to refactor scattered find() calls all over your libraries. You should be doing this anyway, because it definitely helps with improving code and test quality
An excellent gem that can help you with this is Ben Johnson's searchlogic. It gives you a bunch of very useful, canned scopes.
Replace references to RAILS_ENV, RAILS_ROOT, and RAILS_DEFAULT_LOGGER
Thankfully, these ugly constants have no place in a Rails 3 application. There are now methods to access these properties as part of the Rails module. So, for example, you would use Rails.env instead of RAILS_ENV
Nick Quaranto actually just wrote a solid article with the details on the Rails module.