UITextField for Phone Number

Here is my solution.. works great! Formats the phone number in realtime. Note: This is for 10 digit phone numbers. And currently it auto formats it like (xxx) xxx-xxxx.. tweak to your hearts delight.

First in your shouldChangeCharactersInRange you want to gather the whole string for the phone text field and pass it to the validation/formatting function.

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {
NSString* totalString = [NSString stringWithFormat:@"%@%@",textField.text,string];

// if it's the phone number textfield format it.
if(textField.tag==102 ) {
    if (range.length == 1) {
        // Delete button was hit.. so tell the method to delete the last char.
        textField.text = [self formatPhoneNumber:totalString deleteLastChar:YES];
    } else {
        textField.text = [self formatPhoneNumber:totalString deleteLastChar:NO ];
    }
    return false;
}

return YES; 
}

And here is where the phone number is formatted. The regex could probably be cleaned up a bit. But I have tested this code for a while and seems to pass all bells. Notice we also use this function to delete a number in the phone number. Works a little easier here because we already stripped out all the other non digits.

 -(NSString*) formatPhoneNumber:(NSString*) simpleNumber deleteLastChar:(BOOL)deleteLastChar {
if(simpleNumber.length==0) return @"";
// use regex to remove non-digits(including spaces) so we are left with just the numbers 
NSError *error = NULL;
 NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:@"[\\s-\\(\\)]" options:NSRegularExpressionCaseInsensitive error:&error];
 simpleNumber = [regex stringByReplacingMatchesInString:simpleNumber options:0 range:NSMakeRange(0, [simpleNumber length]) withTemplate:@""];

// check if the number is to long
if(simpleNumber.length>10) {
    // remove last extra chars.
    simpleNumber = [simpleNumber substringToIndex:10];
}

if(deleteLastChar) {
    // should we delete the last digit?
    simpleNumber = [simpleNumber substringToIndex:[simpleNumber length] - 1];
}

// 123 456 7890
// format the number.. if it's less then 7 digits.. then use this regex.
if(simpleNumber.length<7)
simpleNumber = [simpleNumber stringByReplacingOccurrencesOfString:@"(\\d{3})(\\d+)"
                                                           withString:@"($1) $2"
                                                              options:NSRegularExpressionSearch
                                                                range:NSMakeRange(0, [simpleNumber length])];

else   // else do this one..
    simpleNumber = [simpleNumber stringByReplacingOccurrencesOfString:@"(\\d{3})(\\d{3})(\\d+)"
                                                           withString:@"($1) $2-$3"
                                                              options:NSRegularExpressionSearch
                                                                range:NSMakeRange(0, [simpleNumber length])];
return simpleNumber;
}