Passing the parameters in actions vector of transaction struct

Question

In the below code, I am passing parameters to actions struct which takes account_name, action_name, permission vector and arguments. But while sending the account_name using N it is taking the exact value of account i.e. account_name not what is the value of this variable. I tried using hard coding the account_name and it worked.

So, the question is how to send the account_name as variable while setting the actions in a transaction.

void send(account_name account, std::string message) { eosio::transaction t{}; t.actions.emplace_back( eosio::permission_level(account, N(active)), N(account), // right now it is sending account as it is, not the value that it contains i.e. eosio N(action), // works fine for this std::make_tuple(message) ); }

Answer 1

So, the question is how to send the account_name as variable while setting the actions in a transaction.

N(account) is a preprocessor macro defined in the eosio codebase to convert the literal string "account" into an uint64_t based on its base32 representation. So, in your case, you only have to use account (which is already uint64_t) instead of N(account).

In the comments, you asked:

In above code, we have to pass the account_name at three different places. 1-in permission_level vector, 2-the second argument and 3-in t.send(). Can you explain me what permissions are these and which account_name i should use and when

As far as I know, there's not much documentation on this, but my understanding is as follows (someone please correct me if I'm wrong):

• The account in permission_level is the account whose permissions are needed to send the action, so you would use the account that would give permission when calling the action
• The second argument is the account to which the action is sent, so you just use the receiver account_name
• The third account is the payer for the transaction for CPU/NET, and this is also contextually chosen based on the service, but typically the same as the account in the first argument (or _self if the contract pays themselves)