Check NSString for special characters

Question

I want to check an NSString for special characters, i.e. anything except a-z, A-Z and 0-9.

I don't need to check how many special characters are present, or their positions, I just need to know whether a particular string contains any or not. If it does, then I want to be able to display "Error!", or something similar.

For example, jHfd9982 is OK but asdJh992@ is not.

Also, letters with accents, diacritics, etc. should not be allowed.

How would I go about this?

Thanks!

Michael

Answer 1

You want to search NSString using a character set if it cant find any characters in the string then rangeOfCharacterFromSet: will return a range of {NSNotFound, 0}

The character set would be like [NSCharacterSet symbolCharacterSet] or your own set. Note you can also invert character sets so you could have a set of acceptable characters

Answer 2

If you want to remove special characters & numbers from any string (even textfield text), while you are editing, these lines below are quite handy:

#define ACCEPTABLE_CHARACTERS @"!~`@#$%^&*-+();:=_{}[],.<>?\\/|\"\'0123456789"

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {

    NSCharacterSet *cs = [NSCharacterSet characterSetWithCharactersInString:ACCEPTABLE_CHARACTERS];

    NSString *filtered = [[string componentsSeparatedByCharactersInSet:cs] componentsJoinedByString:@""];

    return (![string isEqualToString:filtered]) ? NO : YES;
}

Answer 3

NSCharacterSet * set = [[NSCharacterSet characterSetWithCharactersInString:@"abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLKMNOPQRSTUVWXYZ0123456789"] invertedSet];

if ([aString rangeOfCharacterFromSet:set].location != NSNotFound) {
  NSLog(@"This string contains illegal characters");
}

You could also use a regex (this syntax is from RegexKitLite: http://regexkit.sourceforge.net ):

if ([aString isMatchedByRegex:@"[^a-zA-Z0-9]"]) {
  NSLog(@"This string contains illegal characters");
}

Answer 4

Here the code you can use it to check the string has any special character or not

NSString *string = <your string>;

NSString *specialCharacterString = @"!~`@#$%^&*-+();:={}[],.<>?\\/\"\'";
NSCharacterSet *specialCharacterSet = [NSCharacterSet
                                       characterSetWithCharactersInString:specialCharacterString];

if ([string.lowercaseString rangeOfCharacterFromSet:specialCharacterSet].length) {                
    NSLog(@"contains special characters");
}

Answer 5

This code allows only numbers in UITextField input.

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {

    if ([string rangeOfCharacterFromSet:[[NSCharacterSet decimalDigitCharacterSet] invertedSet]].location != NSNotFound)
        return NO;
    else
        return YES;

}