iOS: Formatting number while typing (i.e, Adding commas tu number)

- (void)viewDidLoad {

    [super viewDidLoad];

    self.textField.delegate = self;

}

#pragma mark - UITextFieldDelegate

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

{

         NSString* finalString = [[textField.text stringByReplacingCharactersInRange:range         withString:string] stringByReplacingOccurrencesOfString:@"," withString:@""];

        NSNumber* number =  [[[NSNumberFormatter alloc] init] numberFromString:finalString];

        [textField setText:[NSNumberFormatter localizedStringFromNumber:number numberStyle:NSNumberFormatterDecimalStyle]];

        return NO;

}