A versionable API routing-controller-action strategy.

gistfile1.rb

# Routing
map.with_options(:namespace => 'api/', :path_prefix => "/api/:version", :version => /v\d+/) do |api|
  api.resources :photos
end

# API Controller superclass
class ApiController < ApplicationController
  append_view_path 'views/api'

  # this will happen before anything else that cares about
  # what params[:action] is, even before_filters.
  def perform_action
    params[:action] = @action_name = "#{params[:action]}_#{params[:version]}"
    super
  end
end

# Sample Api controller
class API::PhotosController < ApiController
  def index_v1
    @photos = Photo.all
  end

  def index_v2
    @photos = current_person.photos
  end

  def show_v1
    @photo = Photo.find(params[:id])
  end
  
  def show_v2
    @photo = current_person.photos.find(params[:id])
  end
end

# API views directory structure:
views/
  api/
    photos/
      index_v1.json.erb
      index_v2.json.erb
      show_v1.json.erb
    videos/
      index_v1.json.erb
      show_v1.json.erb