how to log size of array with ilog

Question

I have this code and just want to log size of array:

auto owner = abi_data["owner"].as<chain::authority>();
auto arrSize = std::size(owner.keys);
ilog(arrSize);

But have an error:

error: no matching constructor for initialization of 'fc::log_message'

How can i fix it?

I understand that the c ++ methodology is very specific. Therefore, I will expand my question and thus grope the way.

how to get public key string from auto owner .

i tried:

   std::string k = owner.keys[0].key
   error: no viable conversion from 'eosio::chain::public_key_type' (aka 'fc::crypto::public_key') to 'std::string'

I don't understand how I should transform all this for correct work and get correct public key and replace hardcoded old_account_name .

full code:

else if (action.name == N(newaccount)) {

               auto new_account_name = abi_data["newact"].as<chain::name>().to_string();
               auto creator = abi_data["creator"].as<chain::name>().to_string();
               std::string old_account_name = "EOS7ea3Dj15nUkKz3diU7BmE5FV5aNKsBKL6WScwEaKzNwDp41SSU";
               auto owner = abi_data["owner"].as<chain::authority>();
               auto active = abi_data["active"].as<chain::authority>();
               ilog("new_account_name: " + new_account_name + " ,creator: " + creator);

               *m_session << "UPDATE user_address SET address = :nan WHERE crypto_currency_asset_id = :ai AND address = :oan",
                  soci::use(new_account_name, "nan"),
                  soci::use(old_account_name, "oan"),
                  soci::use(asset_id, "ai");
            }

Answer 1

FIXED!

auto arrSize = sizeof(owner.keys)/sizeof(owner.keys[0]);
auto ownerPK = static_cast<std::string>(owner.keys[0].key);