class ArticlesController < ApplicationController

  def show
    @article = Article.find(params[:id])

    # If the request is stale according to the given timestamp and etag value
    # (i.e. it needs to be processed again) then execute this block
    if stale?(:last_modified => @article.published_at.utc, :etag => @article)
      respond_to do |wants|
        # ... normal response processing
      end
    end

    # If the request is fresh (i.e. it's not modified) then you don't need to do
    # anything. The default render checks for this using the parameters
    # used in the previous call to stale? and will automatically send a
    # :not_modified.  So that's it, you're done.
end

class ArticlesController < ApplicationController

  # This will automatically send back a :not_modified if the request is fresh, and
  # will render the default template (article.*) if it's stale.
  def show
    @article = Article.find(params[:id])
    fresh_when :last_modified => @article.published_at.utc, :etag => @article
  end
end