The much-anticipated Ruby on Rails 1.2 update has shipped, as has the second edition of Agile Web Development with Rails. As our earlier news item mentioned, a major feature of Rails 1.2 is REST (Representational State Transfer) functionality.
I have updated my own Rails installation to version 1.2.1 and have run a full set of tests on local copies of the Rails applications in which I have been involved. I got pages of warnings and feature deprecations. I'm in no hurry to upgrade the production sites, which are running just fine on Rails 1.1, thank you, but I'm planning to use Rails 1.2 for my future Rails sites.
Unless you've been following the Rails evolution or REST itself, REST is probably a new term for you. The term is about 6 years old; it originated in a thesis by Roy Fielding. The following figure from the thesis summarizes how the constraints of Representational State Transfer derive from other architectural styles:
Fielding's thesis is a bit daunting; fortunately, several people have jumped into the breach to explain REST to mere mortals. Many of these articles are listed on the REST Wiki; one of my favorites is REST In Plain English. That article explains how a uniform interface and statelessness look in the real world, or at least in the real Web.
An even better discussion of REST, one that relates directly to Rails 1.2, appears in Chapter 20 of Agile Web Development with Rails. The section from Chapter 12 on creating a REST interface is also quite good, and is available here.
Basically, what Dave Thomas has to say about REST in Chapter 20 is that
"in REST, we use a simple set of verbs to operate on a rich set of nouns. If we're using HTTP, the verbs correspond to HTTP methods (GET, PUT, POST, and DELETE, typically). The nouns are the resources in our application. We name those resources using URLs."
So, the difference between the old way of writing Rails actions and the REST way is that we don't invent a lot of actions with verb phrases as names. Instead, we use standard verbs, and take advantage of Rails' new resource routing facility, embodied in the map.resources keyword to ActionController::Routing::Routes.