While edition 4 of Agile Web Development for Rails was intended to cover
Rails 3.* generically, Rails itself made a large number of user facing changes
between Rails 3.0 and Rails 3.1.  This directory contains the complete source
code for code samples that work with multiple versions of Rails.

The rails30 directory contain samples designed to work with Rails 3.0.5.

The rails31 directory contain samples designed to work with Rails 3.1.0.

The rails32 directory contain samples designed to work with Rails 3.2.3.

The rails40 directory contain samples designed to work with Rails 4.0.0.