How do I set Expires: header when using send_data

Question

I have a method in my controller which uses send_data like this:

def show
  expires_in 10.hours, :public => true
  send_data my_image_generator, :filename => "image.gif", :type => "image/gif"
end

Using expires_in results in headers being sent like this:

HTTP/1.1 200 OK
Connection: close
Date: Fri, 25 Jun 2010 10:41:22 GMT
ETag: "885d75258e9306c46a5dbfe3de44e581"
Content-Transfer-Encoding: binary
X-Runtime: 143
Content-Type: image/gif
Content-Disposition: inline; filename="image.gif"
Content-Length: 1277
Cache-Control: max-age=36000, public

What I would like to do is add an header like Expires: (some exact date) to keep the user agent from revalidating. But I don't see how to make send_data set that header?

I guess I could set it explicitly in the response.headers hash, but surely there must be a wrapper for that (or something)?

Answer 1

Apparently there seems to be no way to pass expires to send_data - instead you must set it yourself in response.headers and take care of formatting the date appropriately:

response.headers["Expires"] = CGI.rfc1123_date(Time.now + period)

Note that the max-age directive in the Cache-Control header overrides the Expires header if both are present. See RFC2616 Section 14.9.3 for more details.

Answer 2

I came across this syntax and I like it :-)

response.headers["Expires"] = 1.year.from_now.httpdate