confusion with contract names and account names in eosio testnet

Question

When writing contracts, the contract class in file name_a.cpp is defined as follows:

class[[eosio::contract("name_a")]] name_b : public contract {..}

In my understanding the name of the class is name_b and the contract is called name_a.

The contract is then deployed to the testnet with the following command with an account named name_c:

cleos -u https://testnet.waxsweden.org set contract name_c /path/to/contract/ name_a.wasm name_a.abi -p name_c@active

What exactly is the name of this contract which must be used for transactions?

My guess would be name_c as this is the name of the account that owns the contract. But what happens with the name specified in [[eosio::contract("name_a")]]? For what is it used?

Answer 1

My guess would be name_c as this is the name of the account that owns the contract.

Correct.

But what happens with the name specified in [[eosio::contract("name_a")]]? For what is it used?

Let's say your headers define multiple contract classes. e.g.

struct [[eosio::contract("contract.1")]] class_1 : eosio::contract
{
   using eosio::contract::contract;
   [[eosio::action]] void act1() {}
};

struct [[eosio::contract("contract.1")]] class_2 : eosio::contract
{
   using eosio::contract::contract;
   [[eosio::action]] void act2() {}
};

struct [[eosio::contract("contract.2")]] class_3 : eosio::contract
{
   using eosio::contract::contract;
   [[eosio::action]] void act3() {}
};

You could do this for multiple reasons:

• You want to split up your code into multiple classes.
• You include another contract's headers to make it easier to create inline actions to it.

The compiler matches the name in [[eosio::contract("name")]] against the command-line option -contract to decide which classes to build into your contract.

e.g. eosio-cpp -contract=contract.1 file.cpp includes act1 and act2 in the contract, while eosio-cpp -contract=contract.2 file.cpp includes act3 instead.