Question

Fast question, i’m using NSPredicate to verify passwords, I already use this code for the username:

-(BOOL)isUserValid:(NSString *)checkString{
    NSString       *filter = @"[A-Z0-9a-z]{5,40}";
    NSPredicate *evaluator = [NSPredicate predicateWithFormat:@"SELF MATCHES %@", filter];
    return [evaluator evaluateWithObject:checkString];
}

But now on the password i would like to allow the user to use special characters such as “@”, “$”, “&”, “*”.

How can i do this?

Answer 1

I don’t know you needs exactly how many characters or specified characters allow to user. but, according to your question example, if you want to allow the user only @,$,&,* characters. refer a following code.

-(BOOL)isUserValid:(NSString *)checkString{
    NSString       *filter = @"[A-Z0-9a-z@$&*]{5,40}";
    NSPredicate *evaluator = [NSPredicate predicateWithFormat:@"SELF MATCHES %@", filter];
    return [evaluator evaluateWithObject:checkString];
}

following filter code is one of the popular password expreesion. alphanumeric characters and select special characters. The password also can not start with a digit, underscore or special character and must contain at least one digit.

Matches password1 | pa$$word2 | pa!@#$%3

Non-Matches password | 1stpassword | $password#

-(BOOL)isUserValid:(NSString *)checkString{
        NSString       *filter = @"^(?=[^\\d_].*?\\d)\\w(\\w|[!@#$%]){5,40}";
        NSPredicate *evaluator = [NSPredicate predicateWithFormat:@"SELF MATCHES %@", filter];
        return [evaluator evaluateWithObject:checkString];
    }

and more expression filter about password. see the site: regexlib_password

following reference is You’ll help while you are working. and remember a following Expression about Character and Bracket.

Character Classes

.   Matches any character except newline. Will also match newline if single-line mode is enabled.
\s  Matches white space characters.
\S  Matches anything but white space characters.
\d  Matches digits. Equivalent to [0-9].
\D  Matches anything but digits. Equivalent to [^0-9].
\w  Matches letters, digits and underscores. Equivalent to [A-Za-z0-9_].
\W  Matches anything but letters, digits and underscores. Equivalent to [^A-Za-z0-9_].
\xff    Matches ASCII hexadecimal character ff.
\x{ffff}    Matches UTF-8 hexadecimal character ffff.
\cA Matches ASCII control character ^A. Control characters are case insensitive.
\132    Matches ASCII octal character 132.

Bracket Expressions

[adf?%] Matches characters a or d or f or ? or %.
[^adf]  Matches anything but characters a, d and f.
[a-f]   Match any lowercase letter between a and f inclusive.
[A-F]   Match any uppercase letter between A and F inclusive.
[0-9]   Match any digit between 0 and 9 inclusive. Does not support using numbers larger than 9, such as [10-20].

[:upper:]   Matches uppercase letters. Equivalent to A-Z.
[:lower:]   Matches lowercase letters. Equivalent to a-z.
[:alpha:]   Matches letters. Equivalent to A-Za-z.
[:alnum:]   Matches letters and digits. Equivalent to A-Za-z0-9.
[:ascii:]   Matches ASCII characters. Equivalent to \x00-\x7f.
[:word:]    Matches letters, digits and underscores. Equivalent to \w.
[:digit:]   Matches digits. Equivalent to 0-9.
[:xdigit:]  Matches characters that can be used in hexadecimal codes. Equivalent to A-Fa-f0-9.
[:punct:]   Matches punctuation.
[:blank:]   Matches space and tab. Equivalent to [ \t].
[:space:]   Matches space, tab and newline. Equivalent to \s.
[:cntrl:]   Matches control characters. Equivalent to [\x00-\x1F\x7F].
[:graph:]   Matches printed characters. Equivalent to [\x21-\x7E].
[:print:]   Matches printed characters and spaces. Equivalent to [\x21-\x7E ].