I've been having problems lately with the atttribution_link urls so i tried making my own regex that works for those too.
Here is my regex string:
(https?://)?(www\\.)?(yotu\\.be/|youtube\\.com/)?((.+/)?(watch(\\?v=|.+&v=))?(v=)?)([\\w_-]{11})(&.+)?
and here are some test cases i've tried:
http://www.youtube.com/watch?v=iwGFalTRHDA
https://www.youtube.com/watch?v=iwGFalTRHDA
http://www.youtube.com/watch?v=iwGFalTRHDA&feature=related
http://youtu.be/iwGFalTRHDA
http://www.youtube.com/embed/watch?feature=player_embedded&v=iwGFalTRHDA
http://www.youtube.com/embed/watch?v=iwGFalTRHDA
http://www.youtube.com/embed/v=iwGFalTRHDA
http://www.youtube.com/watch?feature=player_embedded&v=iwGFalTRHDA
http://www.youtube.com/watch?v=iwGFalTRHDA
www.youtube.com/watch?v=iwGFalTRHDA
www.youtu.be/iwGFalTRHDA
youtu.be/iwGFalTRHDA
youtube.com/watch?v=iwGFalTRHDA
http://www.youtube.com/watch/iwGFalTRHDA
http://www.youtube.com/v/iwGFalTRHDA
http://www.youtube.com/v/i_GFalTRHDA
http://www.youtube.com/watch?v=i-GFalTRHDA&feature=related
http://www.youtube.com/attribution_link?u=/watch?v=aGmiw_rrNxk&feature=share&a=9QlmP1yvjcllp0h3l0NwuA
http://www.youtube.com/attribution_link?a=fF1CWYwxCQ4&u=/watch?v=qYr8opTPSaQ&feature=em-uploademail
http://www.youtube.com/attribution_link?a=fF1CWYwxCQ4&feature=em-uploademail&u=/watch?v=qYr8opTPSaQ
Also remember to check the string you get for your video url, sometimes it may get the percent characters. If so just do this
url = [url stringByReplacingPercentEscapesUsingEncoding:NSUTF8StringEncoding];
and it should fix it.
Remember also that the index of the youtube key is now index 9.
NSRange youtubeKey = [result rangeAtIndex:9]; //the youtube key
NSString * strKey = [url substringWithRange:youtubeKey] ;