iOS: Send If Modified Since header with request

Question

Does anyone know how to send If Modified Since header with a url request?

I'm trying to get a status code back that will tell me if an RSS page has been updated or not.

UPDATE #1: I was able to do a test doing the following:

NSURL *url = [NSURL URLWithString:self.url];
NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url];
[request addValue:@"Tue, 18 Nov 2014 20:46:46 GMT" forHTTPHeaderField:@"If-Modified-Since"];
[NSURLConnection sendAsynchronousRequest:request queue:queue completionHandler:^(NSURLResponse *response, NSData *data, NSError *error) {
    NSHTTPURLResponse *httpResponse = (NSHTTPURLResponse *)response;

    int responseCode = (int)[httpResponse statusCode];
    NSLog(@"All headers: %@", [httpResponse allHeaderFields]);
    NSLog(@"Status code:: %d", responseCode);
}];

What's weird though, if I delete my entire iOS application and run it I get the 304 status code. But, if I comment out the line where I add the If-Modified-Since value and re-run it -- then I get the 200 but when I uncomment that line and re-run it -- then the 304 error doesn't come back... It's a 200 error code. The only way to get the 304 error back is by deleting the entire application off my iPhone device.

Any ideas what's going on?

Check the answer same as here http://stackoverflow.com/questions/31551964/how-to-use-nsurlsession-to-determine-if-resource-has-changed/31567943#31567943 — mkumar, Jul 23 '15 at 10:51
same post as http://stackoverflow.com/questions/31551964/how-to-use-nsurlsession-to-determine-if-resource-has-changed/31567943#31567943 — mkumar, Jul 23 '15 at 10:52

dminones · Answer 1 · 2016-02-15T15:45:06.123

11

A little late with this but since NSURLConnection is caching the responses in order to get the 304 code you should create your request like this.

NSURLRequest *request = [NSURLRequest requestWithURL:url
                                         cachePolicy:NSURLRequestReloadIgnoringCacheData
                                     timeoutInterval:60.0];

edited Feb 15 '16 at 15:45

answered Jan 16 '15 at 20:20

dminones

2,236
20
21

score 0 · Answer 2 · answered Jun 19 '18 at 07:59

304 is not an error!It means the resource is same with your last request. Set the value of this to the Last-Modified value received from the last request to the same endpoint. If the resource has not been updated since the last request, the server will send a 304 (not modified) status code response.

iOS: Send If Modified Since header with request

2 Answers2