Question

I’m using:

+ (BOOL)isPassword:(NSString*)password {
    NSString* pattern = @"^(?=.{6,20}$).*$";
    NSPredicate* predicate = [NSPredicate predicateWithFormat:@"SELF MATCHES %@", pattern];
    return [predicate evaluateWithObject:password];
}

But it is returning yes for "". Any tips?

Answer 1

As @Pfitz pointed out, you don’t have a SELF. That’s used when filtering arrays for instance.

Try using NSRegularExpression instead.

NSError *error = nil;
NSRegularExpression *regex = [NSRegularExpression 
                              regularExpressionWithPattern:@"^(?=.{6,20}$).*$" 
                              options:NSRegularExpressionCaseInsensitive 
                                error:&error];
NSTextCheckingResult *match = [regex firstMatchInString:password 
                                                options:0
                                                  range:NSMakeRange(0, [password length])];
if (match) {
    NSRange range = [match range];
    if (range.location != NSNotFound) {
        // match
    }
}