Iphone: validating string with length minimum 6 characters and having atleast one number

-(BOOL)validatePass:(NSString *)passString{

    if (passString.length >=6) {

        

        NSString *str =passString; // some string to check for at least one digit and a length of at least 7

        if ([str rangeOfCharacterFromSet:[NSCharacterSet decimalDigitCharacterSet]].location != NSNotFound) {

            // this matches the criteria

            return YES;

        }

        else

        {

           return NO;

        }

        

        

        

        

    }

    else{

        return NO;

    }

}