8 Inline Action to External Contract

This section of the guide provides instructions for sending actions to an external contract. The examples of the execution of instructions are shown in the contract, where the performed actions are kept.

8.1 Addressbook counter address contract

Log into CONTRACTS_DIR and create a directory there with the name abcounter, as well as the file abcounter.cpp.

cd CONTRACTS_DIR
mkdir abcounter
cd abcounter
touch abcounter.cpp

Open the abcounter.cpp file and write the following program text into it:

#include <eosiolib/eosio.hpp>

using namespace eosio;

class [[eosio::contract]] abcounter : public eosio::contract {
  private:
    struct [[eosio::table]] counter {
      name key;
      uint64_t emplaced;
      uint64_t modified;
      uint64_t erased;
      uint64_t primary_key() const {
      return key.value;
    }
  };

    using count_index = eosio::multi_index<"counter"_n, counter>;
  public:
    using contract::contract;

    abcounter(name receiver, name code,  datastream<const char*> ds):
contract(receiver, code, ds) {}

    [[eosio::action]]
    void count(name user, std::string type) {
      require_auth( name("addressbook"));
      count_index counts(name(_code), _code.value);
      auto iterator = counts.find(user.value);

      if (iterator == counts.end()) {
        counts.emplace("addressbook"_n, [&]( auto& row ) {
          row.key = user;
          row.emplaced = (type == "emplace") ? 1 : 0;
          row.modified = (type == "modify") ? 1 : 0;
          row.erased = (type == "erase") ? 1 : 0;
        });
      }
      else {
        counts.modify(iterator, "addressbook"_n, [&]( auto& row ) {
          if(type == "emplace") { row.emplaced += 1; }
          if(type == "modify") { row.modified += 1; }
          if(type == "erase") { row.erased += 1; }
        });
      }
    }
};

EOSIO_DISPATCH( abcounter, (count));

The peculiarity of this text is that it has a restriction on calls to an action for the contract account. For restriction, use require_auth for the addressbook contract. Only the addressbook contract account is authorized to perform require_auth. The count action is not sent by the user, but by the addressbook contract.

require_auth( name("addressbook"));

8.2 Create an account for abcounter contract

cleos create account cyber abcounter YOUR_PUBLIC_KEY

8.3 Compile and install the abcounter contract

eosio-cpp -o abcounter.wasm abcounter.cpp --abigen
cleos set contract abcounter CONTRACTS_DIR/abcounter

8.4 Modify the contract addressbook to send inline actions to a new abcounter contract

cd CONTRACTS_DIR/addressbook

Open the file addressbook.cpp and create in it another helper named increment_counter in the private part of the contract.

void increment_counter(name user, std::string type) {

  action counter = action(
    permission_level{get_self(),"active"_n},
    "abcounter"_n,
    "count"_n,
    std::make_tuple(user, type)
  );

  counter.send();
}

The action body contains:

• выдача разрешения уровня active .Для разрешения функция get_self() возвращает текущий контракт addressbook;

• the abcounter account name of the contract;

• the count action to call;

• data, username and line type.

Add calls to «set», «modify» and «erase» helpers.

//Emplace
increment_counter(user, "emplace");
//Modify
increment_counter(user, "modify");
//Erase
increment_counter(user, "erase");

As a result, the addressbook.cpp file should look like this:

#include <eosiolib/eosio.hpp>
#include <eosiolib/print.hpp>

using namespace eosio;

class [[eosio::contract]] addressbook : public eosio::contract {

  private:
    struct [[eosio::table]] person {
      name key;
      std::string first_name;
      std::string last_name;
      uint64_t age;
      std::string street;
      std::string city;
      std::string state;

      uint64_t primary_key() const { return key.value; }

      uint64_t get_secondary_1() const { return age;}

    };

    void send_summary(name user, std::string message) {
      action(
        permission_level{get_self(),"active"_n},
        get_self(),
        "notify"_n,
        std::make_tuple(user, name{user}.to_string() + message)
      ).send();
    };

    void increment_counter(name user, std::string type) {

      action counter = action(
        permission_level{get_self(),"active"_n},
        "abcounter"_n,
        "count"_n,
        std::make_tuple(user, type)
      );

    counter.send();
  }

  typedef eosio::multi_index<"person"_n, person,
    indexed_by<"byage"_n, member<person, uint64_t, &person::get_secondary_1>>
  > address_index;
  public:
    using contract::contract;

    addressbook(name receiver, name code,  datastream<const char*> ds):  contract(receiver, code, ds) {}

    [[eosio::action]]
    void upsert(name user, std::string first_name, std::string last_name, uint64_t age, std::string street, std::string city, std::string state) {
      require_auth(user);
      address_index addresses(_code, _code.value);
      auto iterator = addresses.find(user.value);
      if( iterator == addresses.end() )
      {
        addresses.emplace(user, [&]( auto& row ) {
         row.key = user;
         row.first_name = first_name;
         row.last_name = last_name;
         row.age = age;
         row.street = street;
         row.city = city;
         row.state = state;

         send_summary(user, " successfully emplaced record to addressbook");
         increment_counter(user, "emplace");
        });
      }
      else {
        std::string changes;
        addresses.modify(iterator, user, [&]( auto& row ) {
          row.key = user;
          row.first_name = first_name;
          row.last_name = last_name;
          row.age = age;
          row.street = street;
          row.city = city;
          row.state = state;

          send_summary(user, " successfully modified record to addressbook");
          increment_counter(user, "modify");
      });

    }
  }

  [[eosio::action]]
    void erase(name user) {
      require_auth(user);

      address_index addresses(_code, _code.value);
      auto iterator = addresses.find(user.value);
      eosio_assert(iterator != addresses.end(), "Record does not exist");
      addresses.erase(iterator);
      send_summary(user, " successfully erased record from addressbook");
      increment_counter(user, "erase");
    }

  [[eosio::action]]
    void notify(name user, std::string msg) {
      require_auth(get_self());
      require_recipient(user);
    }

  };

EOSIO_DISPATCH( addressbook, (upsert)(notify)(erase));

8.5 Recompile and set the addressbook contract

Since the changes should not affect the ABI, you do not need to re-edit the ABI file (make sure that this file has not been updated).

eosio-cpp -o addressbook.wasm addressbook.cpp
cleos set contract addressbook CONTRACTS_DIR/addressbook

8.6 Perform testing of sending an action from an addressbook contract to an abcounter contract

Before testing, make sure that the abcounter and addressbook contracts are set.

8.6.1 Verify that a notification is sent to the abcounter contract, as well as a change in the entry in the addressbook contract table by executing:

cleos push action addressbook upsert '["alice", "alice", "liddell", 19, "123 drink me way", "wonderland", "amsterdam"]' -p alice@active

The action is considered successful if the output contains the following information:

executed transaction: ...
#   addressbook <= addressbook::upsert          {"user":"alice","first_name":"alice","last_name":"liddell","street":"123 drink me way","city":"wonde...
#   addressbook <= addressbook::notify          {"user":"alice","msg":"alice successfully modified record in addressbook"}
#         alice <= addressbook::notify          {"user":"alice","msg":"alice successfully modified record in addressbook"}
#     abcounter <= abcounter::count             {"user":"alice","type":"modify"}

8.6.2 Check the appearance of a row in the table for the alice user.

cleos get table abcounter abcounter counts --lower alice --limit 1

The action is considered successful if the result is the following:

{
  "rows": [{
      "key": "alice",
      "emplaced": 1,
      "modified": 0,
      "erased": 0
    }
  ],
  "more": false
}

8.6.3 Check that the upsert method modifies the record.

cleos push action addressbook upsert '["alice", "alice", "liddell", 21,"1 there we go", "wonderland", "amsterdam"]' -p alice@active

The actions are considered successfully completed if the resulting output contains the following information:

executed transaction: …
#   addressbook <= addressbook::upsert          {"user":"alice","first_name":"alice","last_name":"liddell","street":"1 coming down","city":"normalla...
#   addressbook <= addressbook::notify          {"user":"alice","msg":"alice successfully emplaced record to addressbook"}
>> Notified
#         alice <= addressbook::notify          {"user":"alice","msg":"alice successfully emplaced record to addressbook"}
#     abcounter <= abcounter::count             {"user":"alice","type":"emplace"}
warning: transaction executed locally, but may not be confirmed by the network yet    ]

8.6.4 Verify the liquidation of the alice user entry from the table by running:

cleos push action addressbook erase '["alice"]' -p alice@active

The action is considered to be successfully completed if the resulting output contains the following information:

executed transaction: ...
#   addressbook <= addressbook::erase           {"user":"alice"}
>> Erased
#   addressbook <= addressbook::notify          {"user":"alice","msg":"alice successfully erased record from addressbook"}
>> Notified
#         alice <= addressbook::notify          {"user":"alice","msg":"alice successfully erased record from addressbook"}
#     abcounter <= abcounter::count             {"user":"alice","type":"erase"}
warning: transaction executed locally, but may not be confirmed by the network yet    ]
Toaster:addressbook sandwich$

8.6.5 Test the ability to manipulate abcounter contract data by executing:

cleos push action abcounter count '["alice", "erase"]' -p alice@active
cleos get table abcounter abcounter counts --lower alice

The abcounter contract table should contain the following information:

{
  "rows": [{
      "key": "alice",
      "emplaced": 1,
      "modified": 1,
      "erased": 1
    }
  ],
  "more": false
}