Hello contract: How do i execute "hi" action when notified by eosio.token contract of an EOS transfer?

Question

I want to extend the Hello contract (as an exercise)

How do i execute "hi" action when notified by eosio.token contract of an EOS transfer ?

I understood i have to extend EOSIO_ABI macro to handle eosio.token transfer notification, but i cannot get it working.

Thank you

Answer 1

I finally found a way by redefining EOSIO_ABI.

The "transfer" function in my contract get called when an EOS transfer is done through eosio.token contract.

#undef EOSIO_ABI
#define EOSIO_ABI( TYPE, MEMBERS ) \
extern "C" { \
  void apply( uint64_t receiver, uint64_t code, uint64_t action ) { \
     if( action == N(onerror)) { \
     /* onerror is only valid if it is for the "eosio" code account and authorized by "eosio"'s "active permission */ \
     eosio_assert(code == N(eosio), "onerror action's are only valid from the \"eosio\" system account"); \
  } \
  auto self = receiver; \
  if( code == self || code == N(eosio.token) || action == N(onerror) ) { \
     TYPE thiscontract( self ); \
     switch( action ) { \
        EOSIO_API( TYPE, MEMBERS ) \
     } \
     /* does not allow destructor of thiscontract to run: eosio_exit(0); */ \
     } \
  } \
}

 EOSIO_ABI(ping_contract, (ping) (transfer) )

I used something like this for the permission:

cleos set account permission CONTRACT_ACCOUNT active '{"threshold": 1,"keys": [{"key":"CONTRACT_ACCOUNT_PUBKEY","weight":1}],"accounts": [{"permission":{"actor":"CONTRACT_ACCOUNT","permission":"eosio.code"},"weight":1}]}' owner -p CONTRACT_ACCOUNT@active