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

{

    if (!string.length)

    {

        return YES;

    }

    if (textField.keyboardType == UIKeyboardTypeNumberPad)

    {

        if ([string rangeOfCharacterFromSet:[[NSCharacterSet decimalDigitCharacterSet] invertedSet]].location != NSNotFound)

        {

            return NO;

        }

    }

    NSString *updatedText = [textField.text stringByReplacingCharactersInRange:range withString:string];

    if (updatedText.length > ) // 4 was chosen for SSN verification

    {

        if (string.length > )

        {

            // BasicAlert(@"", @"This field accepts a maximum of 4 characters.");

        }

        return NO;

    }

    return YES;

}