NSURLCache on iOS 4.3.x not checking Last-Modified or Etag headers

Question

If I download a document using NSURLConnection/NSURLCache that gets cached, edit that document on the server (so Last-Modified and Etag headers change) and then download the document again, the previously cache version is returned. NSURLCache/NSURLConnection makes no attempt to check for a newer resource using If-Modified-Since/If-None-Match headers in the request (which would return a newer version of the resource).

SHould NSURLCache used in conjunction with NSURLConnection check for an updated resource on the server using Last-Modified/Etag headers that have been previously cached? I can't seem to find any documentation to say whether this should happen or if checking for HTTP 304 content is up to the developer.

Answer 1

I'll let other people comment on how to use NSURLCache. I found that the most reliable way to prevent caching with NSURLConnection, proxy servers, and misconfigured web servers, was to append an incrementing number to your URL.

So rather than using http://mycompany.com/path, use http://mycompany.com/path?c=1, http://mycompany.com/path?c=2, http://mycompany.com/path?c=3, etc, etc.

It's a hack, but a good one.