Problem with regex detecting $<name>

Question

I am trying to detect the following expression: $

for example

$john

or

$mike

What is wrong with my regex?

//Check for $symbol
    NSRegularExpression *symbolRegex = [[NSRegularExpression alloc] initWithPattern:@"($[a-zA-Z0-9_]+)" 
                                                                              options:NSRegularExpressionCaseInsensitive 
                                                                                error:nil];
    matches = [symbolRegex matchesInString:labelText options:0 range:NSMakeRange(0, [labelText length])];

    for (NSTextCheckingResult *result in matches) {
        NSURL *url = [NSURL URLWithString:[NSString stringWithFormat:@"symbol://%@",[labelText substringWithRange:result.range]]];
        [bodyLabel addCustomLink:url inRange:[result range]];        
    }

    [symbolRegex release];

csano · Accepted Answer · 2011-08-17 00:23:41Z

3

It looks like you need to escape the $.

(\\$[a-zA-Z0-9_]+)

$ (dollar)

Matches at the end of the string the regex pattern is applied to. Matches a position rather than a character. Most regex flavors have an option to make the dollar match before line breaks (i.e. at the end of a line in a file) as well. Also matches before the very last line break if the string ends with a line break.

Since it's a special/reserved character, it needs to be escaped.

http://www.regular-expressions.info/reference.html

edited Aug 17, 2011 at 0:23

answered Aug 16, 2011 at 23:53

csano

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5 Comments

Sheehan Alam Over a year ago

I get the compiler warning: Unknown escape sequence '\$'

csano Over a year ago

You have to escape the backslash. Try \\$.

Sheehan Alam Over a year ago

No more warning, but the code is not detecting $john type text

csano Over a year ago

What does the string look like? Just "$john"? Are you getting an error of any sort?

Sheehan Alam Over a year ago

There are no matches, so my matches array is empty.

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