module ActionDispatch::Http::URL

def protocol

req.protocol # => "https://"
req = ActionDispatch::Request.new 'HTTP_HOST' => 'example.com', 'HTTPS' => 'on'

req.protocol # => "http://"
req = ActionDispatch::Request.new 'HTTP_HOST' => 'example.com'

Returns 'https://' if this is an SSL request and 'http://' otherwise. 
def protocol
  @protocol ||= ssl? ? "https://" : "http://"
end