二代身份证除了位数和各位表达的含义有限制外，还有一个校验和的问题，这篇文章就是来解决这个问题。网络上应该有对应的Java代码，我在这里这是把Java代码转换成了oc的代码，供大家使用。已经经过测试，验证正确。

- (BOOL)validateIdentityCard:(NSString *)identityCard
{
  BOOL flag;
  if (identityCard.length <= 0) {
      flag = NO;
      return flag;
  }

  flag = [identityCardPredicate evaluateWithObject:identityCard];

  flag = flag && [self isRealIDCode:identityCard];

  return flag;

}

- (BOOL)isRealIDCode:(NSString *)realCode {

  if (realCode.length < 18) {
      return false;
  }

  NSArray *ds = @[@7, @9, @10, @5, @8, @4, @2, @1, @6, @3, @7, @9, @10, @5, @8, @4, @2];
  NSInteger total = 0;

  for (NSInteger i = 0; i < 17; i++) {
    
      NSRange currentRange = NSMakeRange(i, 1);
      NSString *currentCode = [realCode substringWithRange:currentRange];
      NSInteger currentCodeInteger = [currentCode integerValue];
    
      NSInteger dsi = [ds[i] integerValue];
      total += currentCodeInteger * dsi;
  }

  total = total % 11;
  NSArray *ends = @[@"1", @"0", @"x", @"9", @"8", @"7", @"6", @"5", @"4", @"3", @"2"];
  NSString *end = ends[total];

  if ([end isEqualToString:[[realCode substringWithRange:NSMakeRange(17, 1)] lowercaseString]]) {
      return YES;
  }

  return NO;
}