How to make regular expressions in objC

lol.m

static inline NSRegularExpression * TagRegularExpression() {
    static NSRegularExpression *_tagRegularExpression = nil;
    
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        _tagRegularExpression = [[NSRegularExpression alloc] initWithPattern:@"\\#[\\w]+"
                                                                     options:NSRegularExpressionCaseInsensitive
                                                                       error:nil];
    });
    
    return _tagRegularExpression;
}