Return token to owner after initiating a transfer to my contract

Question

Good Day,

I am working on a contract where for example, If I send 2 ETH to a contract, ( 1 ETH = 2 Cryptokitty tokens ) then that contract is supposed to return me 4 Cryptokitty tokens.

What I Have done so far

So far, I am able to transfer the funds from my account to the contract, but I am unsure how to automatically transfer back X amount of funds to the person who sent the 2 Eth.

This is my code called when a transfer takes place on this account.

  [[eosio::on_notify("eosio.token::transfer")]]
  void fundpurchase(name from, name to, asset quantity, std::string memo){

  //Bunch of other code which was removed for simplicity. 


      });

My question is, when I execute

cleos transfer peter bigger "2 CRYCOIN" "memooo" -p peter@active

How can I make it so that, I automatically transfer something back to Peter's account.

Answer 1

You need to construct the action and send it. It depends on if you are using multiple or a single contract and some props. Something like this should work:

[[eosio::on_notify("eosio.token::transfer")]]
  void fundpurchase(name from, name to, asset quantity, std::string memo){
  action(
    permission_level {_self,N(active)},
    N(eosio.token),N(transfer),
    std::make_tuple(_self,N(YOURTOKEN_CONTRACT),asset(quantity.amount*2,symbol_type(S(4,YOURTOKEN))),std::string("some memo"))
   ).send();
}