What does require_auth (_self) do in EOS?

Question

I have seen in numerous places that the following is coded -

require_auth (_self);

Aside from the intuitive meaning that it requires a user to be authorised, what exactly does it do and how?

Answer 1

Contracts inherit from eosio::contract, and, if we look in eosiolib/contract.hpp for the base class, we see that the constructor for eosio::contract is as follows:

contract( account_name n ):_self(n){}

Therefore, the account that creates the contract and calls the constructor becomes _self. Thus, require_auth(_self) ensures that the account executing the function has the authority of the account that created the contract.