Filtering characters entered into a UITextField

Question

I have a UITextField in my application. I\'d like to restrict the set of characters that can be can be entered into the field to a set that I have defined. I could filter th

Answer 1

Here is one of the cleanest approaches to restricting characters entered in a UITextField. This approach allows the use of multiple predefined NSCharacterSets.

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

    NSMutableCharacterSet *allowedCharacters = [NSMutableCharacterSet alphanumericCharacterSet];
    [allowedCharacters formUnionWithCharacterSet:[NSCharacterSet whitespaceCharacterSet]];
    [allowedCharacters formUnionWithCharacterSet:[NSCharacterSet symbolCharacterSet]];

    if([string rangeOfCharacterFromSet:allowedCharacters.invertedSet].location == NSNotFound){

        return YES;

    }

    return NO;

}