class ApplicationController < ActionController::Base
  # ...

  def serve_attachment(model, filename)
    case RAILS_ENV
    when 'development'
      redirect_to model.attachment_url(filename)
    when 'production'
      response.headers['Content-Type'] = model["_attachments"][filename]['content_type']
      response.headers['Content-Disposition'] = "inline; filename=#{filename}"
      response.headers['X-Accel-Redirect'] = "/couch/#{model.id}/#{filename}"
      render :nothing => true
    else
      metadata = model["_attachments"][filename]
      data = model.fetch_attachment(filename)
      send_data(data, {
        :filename    => filename,
        :type        => metadata['content_type'],
        :disposition => "inline"
      })
    end
  end
end