Regular expression to grub usernames from string

Question

i need to find usernames (like twitter ones) in strings, for example, if the string is:

"Hello, @username! How are you? And @username2??"

I want to isolate/extract @username and @username2

Do you know how to do it in Objective-C, i found this for Python regex for Twitter username but does not work for me

I tried it like this, but is not working:

NSString *comment = @"Hello, @username! How are you? And @username2??";

NSError *error = nil;
NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:@"(?<=^|(?<=[^a-zA-Z0-9-\\.]))@([A-Za-z]+[A-Za-z0-9-]+)" options:0 error:&error];
NSArray *matches = [regex matchesInString:comment options:0 range:NSMakeRange(0, comment.length)];
for (NSTextCheckingResult *match in matches) {
    NSRange wordRange = [match rangeAtIndex:1];
    NSString *username = [comment substringWithRange:wordRange];
    NSLog(@"searchUsersInComment result --> %@", username);
}

please don't post new questions. It will lead to duplicate questions. Edit your old question adding details of what worked and what didn't. Then people will able to reopen your question. — Teja Nandamuri, Jun 08 '16 at 15:25
Yes, but my old question was marked as DUPLICATE and closed, i had to open a new one — alfreedom, Jun 08 '16 at 15:25
all of it, that function does not grub anything... try run the example i wrote — alfreedom, Jun 08 '16 at 15:30

Teja Nandamuri · Accepted Answer · 2016-06-08T15:34:54.840

(?<=^|(?<=[^a-zA-Z0-9-\\.]))@([A-Za-z]+[A-Za-z0-9-]+) is to neglect emails and grab only usernames, as your string doesn't contain any emails, you should just use @([A-Za-z]+[A-Za-z0-9-]+)

Your regex is wrong. You need to modify it to:

  NSString *comment = @"Hello, @username! How are you? And @username2??";

    NSError *error = nil;
    NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:@"@([A-Za-z]+[A-Za-z0-9-]+)" options:0 error:&error];
    NSArray *matches = [regex matchesInString:comment options:0 range:NSMakeRange(0, comment.length)];
    for (NSTextCheckingResult *match in matches) {
        NSRange wordRange = [match rangeAtIndex:1];
        NSString *username = [comment substringWithRange:wordRange];
        NSLog(@"searchUsersInComment result --> %@", username);
    }

FYI: Any subpattern inside a pair of parentheses will be captured as a group. In practice, this can be used to extract information like phone numbers or emails from all sorts of data. Imagine for example that you had a command line tool to list all the image files you have in the cloud. You could then use a pattern such as ^(IMG\d+.png)$ to capture and extract the full filename, but if you only wanted to capture the filename without the extension, you could use the pattern ^(IMG\d+).png$ which only captures the part before the period.

I would suggest you to read about regex strings: http://regexone.com/lesson/capturing_groups

Also, `(?<=^|(?<=[^a-zA-Z0-9-\\.]))` is excessively creative. `(?<![a-zA-Z0-9-\\.])` does the same thing. — Alan Moore, Jun 10 '16 at 12:44

Regular expression to grub usernames from string

1 Answers1