I use exact gem versions because experience shows that even minor gem updates can break the tutorial. (RSpec is particularly guilty of this.) I generally recommend '~>' for more advanced users, but when getting your bearings I think it's best to use exact versions.

That said, I keep the Rails Tutorial and sample application as up-to-date as possible—and in fact both have already been updated with the latest version. :-)

http://ruby.railstutorial.org/ruby-on-rails-tutorial-book#se...

    $ gem install rails -v 3.2.12

https://github.com/railstutorial/sample_app_2nd_ed/blob/mast...

    gem 'rails', '3.2.12'