Locomotivation

Step 1: Register your custom mime type

The first thing we need to do is tell Rails we’ve got a new format type to serve up:

# config/environment.rb

Mime::Type.register_alias "text/html", :iphone
Mime::Type.register_alias "text/html", :beta

We used beta, but you could use any value here not already in use.

Step 2: Detect a beta request

In order to let only the cool folks into our new beta site, we’ll need a big burly bouncer at the door keeping out the riff-raff:

# application.rb
before_filter :adjust_format_for_beta

...

def adjust_format_for_beta
  request.format = :beta if beta_request? 
end

def beta_request?
  return (request.subdomains.first == "beta" || params[:format] == "beta")
end

The before_filter executes before each request and if ‘beta’ is the first subdomain or passed in as a format param, Rails will set the format to :beta.

Step 3: We’re in da club, now what?

Once we’ve identified our beta users, we now need to give them the new eye candy. We do this simply by dropping in a new view named xxxxxx.beta.erb. The bulk of the changes for our redesign are in a new application layout which serves up a new basic layout and CSS.

application.html.erb → application.beta.rb

Other views (even partials) are swapped out in a similar manner:

show.html.erb → show.beta.erb

_lesson.html.erb → _lesson.beta.erb

And that’s it! You don’t have to do every view in the site because Rails will fall back to .html.erb for any views without a .beta.erb version. Most of our redesign is accomplished in CSS. Where we have massive markup changes, we simply swap out the view templates.

See update 2 below

A gotcha to watch out for

In a few cases, we had respond_to blocks in our controllers to handle differences between the iPhone and regular versions of the site. Anywhere that you have these, you’ll need to add the beta mime type as well:

respond_to do |format|
  format.html
  format.beta # <= You'll get a 406 Unprocessable entity error without this line
  format.iphone do 
    render :layout => false if request.xhr?
  end
end

If an action does not already have a respond_to block, you’re OK. No changes are required in your controller.

UPDATE

Thanks, Ryan Heneise, for reminding me about the last step:

Step 4: What is new is old again

When you’re ready to launch, you’ll want to fold all those beta views back into your project as the default .html.erb views. Simply rename them from .beta.erb to .html.erb. For us, it’s a bit easier since we don’t have to overwrite any .html.erb files. We’re still using .rhtml!

Thanks, Ryan!

UPDATE 2

Paul Canavese turns in some excellent QA work and informs me that Rails will not fall back to .html.erb. Our templates are still .rhtml. So it would appear you will have to touch each template or use .rhtml. Sorry!