NSRegularExpression not working - objective-c

Question

I'm try to parse a photo id out of a facebook url, e.g.,
https://www.facebook.com/photo.php?fbid=267217740038587&set=a.207272412699787.48907.100002510899673&type=1
My regex is #"https?:\/\/(www\.)?facebook\.com\/photo\.php\?fbid=([0-9]+)"
I tested this with an external tool RegExhibit - http://homepage.mac.com/roger_jolly/software/ and it seems to work fine.
However it does not work in XCode. I tried to debug and the problem seems to be the \? after photo\.php. When I change it to
#"https?:\/\/(www\.)?facebook\.com\/photo\.php.fbid=([0-9]+)" (notice I change \? to .)
it works perfectly.
While this is acceptable I would like to know why \? doesn't work here. Any expert? :-)

Answer 1

I'm not sure, but perhaps the back slashes \ are escaping the relevant following character in the NSString itself when it is parsed. For instance,
NSLog(#"https?:\/\/(www\.)?facebook\.com\/photo\.php\?fbid=([0-9]+)");
actually prints https?://(www.)?facebook.com/photo.php?fbid=([0-9]+) which if then treated as its own regex would execute the way you describe it (and does execute semi-properly if you replace the ? with a .)
So, I'm guessing for it to work properly, you'd need #"https?:\\/\\/(www\\.)?facebook\\.com\\/photo\\.php\\?fbid=([0-9]+)" instead.

Answer 2

You can try this:
NSString *query = #"parameter=2&secondparameter=3"; // replace this with [url query];
NSArray *components = [query componentsSeparatedByString:#"&"];
NSMutableDictionary *parameters = [[NSMutableDictionary alloc] init];
for (NSString *component in components) {
[parameters setObject:[[component componentsSeparatedByString:#"="] objectAtIndex:0] forKey:[[component componentsSeparatedByString:#"="] objectAtIndex:1]];
}