What's wrong with this Objective-C regex?

Question

I'm trying to detect any words between asterisks:

NSString *questionString = @"hello *world*";
NSMutableAttributedString *goodText = [[NSMutableAttributedString alloc] initWithString:questionString]; //should turn the word "world" blue

    NSRange range = [questionString rangeOfString:@"\\b\\*(.+?)\\*\\b" options:NSRegularExpressionSearch|NSCaseInsensitiveSearch];
    if (range.location != NSNotFound) {
        DLog(@"found a word within asterisks - this never happens");
        [goodText addAttribute:NSForegroundColorAttributeName value:[UIColor blueColor] range:range];
    }

But I never get a positive result. What's wrong with the regex?

Answer 1

@"\\B\\*([^*]+)\\*\\B"

should achieve what you expect.

You have to use \B in place of \b for word boundaries, as per Difference between \b and \B in regex.

Finally, using [^*]+ matches each pair of asterisks, instead of the outermost only.

For instance, in the string

Hello *world* how *are* you

it will correctly match world and are, instead of world how are.

Another way for achieving the same is using ? which will make the + non-greedy.

@"\\B\\*(.+?)\\*\\B"

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Also it's worth noting that rangeOfString:options returns the range of the first match, whereas if you are interested in all the matches you have to use build a NSRegularExpression instance with that pattern and use its matchesInString:options:range: method.