Question

In my iPad app. I have one UITextField. User would enter some value in that text field. This value has to be Alpha Numeric. I want to show an alert to the user if he/she enters any special character.
How can I do it? What should be the condition for alert?

Any help would be highly appreciated.

Thanks and regards,
PC

Answer 1

Implement textField:shouldChangeCharactersInRange:replacementString: in the delegate, check the replacement string for special characters, and disallow the replacement if you detect any.

The easiest way to check for non-alphanumerics is as follows:

if ([replacementString rangeOfCharacterFromSet:[[NSCharacterSet alphanumericCharacterSet] invertedSet]].location != NSNotFound) {
    // There are non-alphanumeric characters in the replacement string
}