NSRegularExpression for hashtags and mentions with special characters?

Question

I'm using the following regex expression to detect hashtags and mentions in my app.

NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:@"(#|@)(\\w+)" options:NSRegularExpressionCaseInsensitive error:&error];

However users within my app are allowed to use some special characters in their usernames. For example @user.name or @user_name. Spaces are not allowed. However using thins regular expression would only detect @user when it should in fact be @user.name. Hostages work perfectly but the special characters in usernames break the mention functionality.

I'm really new to regex and I'm not sure what I need to change to fix this. I'm pretty sure its something to do \\w+ but what exactly I could do with some help.

Answer 1

Since you need to match any non-whitespace characters after @ or # but the last character of this sequence must be a word character, you can safely use

@"[#@]\\S+\\b"

Note that an alternative group (#|@) works more effeciently when transformed into a character class [#@] (it involves less backtracking).

Regex breakdown:

• [#@] - match a # or @, 1 time
• \S+\b - match 1 or more non-whitespace characters but the last one must be at the word boundary.

A bit more enhanced version (to make sure the first character after #/@ is a word character and the whole username is at least 1 character long):

@"[#@]\\w\\S*\\b"

Note that this second version will not support such names as @-nick.name-.