HH:MM:SS Formatting for UITextField

gistfile1.m

- (void)viewDidLoad:(BOOL)animated {
  [super viewDidLoad:animated];

  self.numberFormatter = [[NSNumberFormatter alloc] init];
  [self.numberFormatter setNumberStyle:NSNumberFormatterNoStyle];
  [self.numberFormatter setGroupingSize:2];
  [self.numberFormatter setGroupingSeparator:@":"];
  [self.numberFormatter setUsesGroupingSeparator:YES];
  [self.numberFormatter setMaximumFractionDigits:0];
  [self.numberFormatter setMinimumIntegerDigits:6];
  [self.numberFormatter setMaximumIntegerDigits:6];

  NSInteger time = 10800;
  NSInteger hours = (time / 3600) % 3600;
  NSInteger minutes = (time / 60) % 60;
  NSInteger seconds = time % 60;

  self.textField.delegate = self;
  self.textField.text = [self.numberFormatter stringFromNumber:@([[NSString stringWithFormat:@"%02d%02d%02d", hours, minutes, seconds] doubleValue])];
}

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)replacementString {
  NSString *originalNumber = textField.text;
  if([replacementString isEqualToString:@""]) {
    originalNumber = [originalNumber stringByReplacingCharactersInRange:range withString:@""];
  } else {
    originalNumber = [originalNumber stringByAppendingString:replacementString];
  }
  originalNumber = [originalNumber stringByReplacingOccurrencesOfString:@":" withString:@""];
  NSString *newString = [self.numberFormatter stringFromNumber:[NSNumber numberWithDouble:[originalNumber doubleValue]]];
  self.textField.text = newString;

  return NO;
}