In-app rails redirect from root / top to www

Question

Due to the fact that when using the endpoint SSL I installed, I installed DNSimple the Alias , to give me the URL-root function.

Now I have both the root and www versions of the site and it works via SSL, but I would like to redirect all this to www., Which the hero suggests doing in the application itself (Rails 3.2).

Here are some suggestions you can use to do this:

• add before_filter file to application_controller.rb
• redirect route.rb file
• use a gem like this: https://github.com/jtrupiano/rack-rewrite

So what is the best / recommended way to redirect the root URL to www (including https) in Rails? Details are appreciated, as most examples show how to do this the other way around.