A method to try and retrieve the Youtube video ID from a string. (designed to parse user input, hence the multiple accepted formats).

gistfile1.m

/// Accepts any of the following formats
//
// - The Youtube ID itself:
// 1. yj4OtpHl8EE
//
// - A youtu.be short URL:
// 2. http://youtu.be/yj4OtpHl8EE
//
// - A normal youtube.com URL:
// 3. http://www.youtube.com/watch?v=ZvmMzI0X7fE
// 
// - A complex youtube.com URL
// 4. https://www.youtube.com/watch?v=mHeo62B0d0E&index=13&list=FLJ6Kj3NntkXiV-u2TTBO9w
//



-(NSString*)youtubeIDForString:(NSString*)inputString{
	NSString *videoIDString = inputString;
	
	BOOL httpFound = [videoIDString rangeOfString:@"http"].location != NSNotFound;
	BOOL wwwFound = [videoIDString rangeOfString:@"www"].location != NSNotFound;
	BOOL comFound = [videoIDString rangeOfString:@"com"].location != NSNotFound;
	BOOL slashFound = [videoIDString rangeOfString:@"/"].location != NSNotFound;
	
	if (slashFound || comFound || wwwFound || httpFound) {
		// It is likely a URL
		
		BOOL vFound = [videoIDString rangeOfString:@"v="].location != NSNotFound;
		if (vFound) {
			// We found the v=, now parse the URL
			NSRange vRange = [videoIDString rangeOfString:@"v="];
			NSMutableString *string = videoIDString.mutableCopy;
			[string replaceCharactersInRange:NSMakeRange(0, vRange.location) withString:@""];
			
			NSMutableDictionary *keyValues = [NSMutableDictionary dictionary];
			
			NSArray *stringParts = [string componentsSeparatedByString:@"&"];
			if (stringParts.count > 0) {
				for (NSString *subString in stringParts) {
					NSArray *keyValue = [subString componentsSeparatedByString:@"="];
					if (keyValue.count == 2) {
						[keyValues setValue:[keyValue objectAtIndex:1] forKey:[keyValue objectAtIndex:0]];
					}
				}
			}
			
			return keyValues[@"v"];
		}
		else {
			NSArray *stringParts = [videoIDString componentsSeparatedByString:@"/"];
			return stringParts.lastObject;
		}
	}
	else if (videoIDString.length > 0) {
		return videoIDString;
	}
	
	return nil;
}