Smart Contract (assets)

We will now describe the set of actions and table structures to implement the dGoods standard. In this section we focus on assets-related actions and tables. In the next section we will talk about dGoods’ built-in decentralized exchange.

Tables

class dgoods

TABLE tokenconfigs

// scope is self
eosio::symbol_code symbol;
eosio::name standard;
string version;
uint64_t category_name_id;

The first table created and must be initialized with setconfig() before any tokens can be created. tokenconfigs is a singleton which holds the basic information for the contract including

• symbol for the contract

• standard and version that let wallets know what they need to support for this contract

• category_name_id which is like a global id for category:token_name pairs; the value will increment by one every time create() is successfully executed

TABLE dgoodstats

// scope is category
bool fungible;
bool burnable;
bool sellable;
bool transferable;
eosio::name issuer;
eosio::name token_name; // primary key
uint64_t category_name_id;
eosio::asset max_supply;
eosio::asset current_supply;
eosio::asset issued_supply;
eosio::name rev_partner;
double rev_split;
string base_uri;

Saves token info such as

• if the token is fungible, burnable, sellable and transferable

• the issuer account who is authorized to issue the token

• category (as table scope) and token_name to determine token classfication; the pair category:token_name must be unique

• category_name_id which is like a global id for category:token_name

• max_supply, current_supply, issued_supply given as eosio::asset; for NFTs the precision must be integer; issued_supply is used to keep track of unique id’s when tokens are burned as it never decreases

• rev_partner and rev_split which are used to determine how to split the income when the token is sold in the built-in Decentralized Exchange

• base_uri will be used together with relative_uri from table dgood to provide extra metadata for the token, usually as one of metadata templates

Info is written when a token is created. The category is used as table scope and token_name is the primary key, so it ensures each category:token_name pair is unique.

TABLE categoryinfo

// scope is self
eosio::name category; // primary key

Holds all category names for easy querying.

TABLE dgood

// scope is self
uint64_t id; // primary key
uint64_t serial_number;
eosio::name owner; // secondary key
eosio::name category;
eosio::name token_name;
std::optional<string> relative_uri;

The global list for non and semi-fungible tokens. Fungible tokens are not be saved in this table. Secondary indices are used to search by owner.

• relative_uri will be used together with base_uri from table dgoodstats to provide extra metadata for the token, usually as one of metadata templates

TABLE accounts

// scope is owner
uint64_t category_name_id; // primary key
eosio::name category;
eosio::name token_name;
eosio::asset amount;

Holds account information. For fungible tokens amount is the token balance while for NFTs it is the number of owned NFTs. Users need to query table dgood to find information for each NFT they own.

Actions

class dgoods

ACTION setconfig(eosio::symbol_code sym, string version)

Must be called first to initialize table tokenconfigs with a symbol and version of dGoods spec. It also initializes category_name_id to zero. Can be called again to update the version but the symbol will not change.

ACTION create(eosio::name issuer, eosio::name rev_partner, eosio::name category, eosio::name token_name, bool fungible, bool burnable, bool sellable, bool transferable, double rev_split, string base_uri, eosio::asset max_supply)

Defines a type of token before any tokens can be issued. See table dgoodstats of how properties are defined.

ACTION issue(eosio::name to, eosio::name category, eosio::name token_name, eosio::asset quantity, string relative_uri, string memo)

Mints a token and gives ownership to the to account. The token category:token_name must be created first. quantity must match the symbol and precision of max_supply. fixme For NFTs, can issue up to 100 at one time.

ACTION transferft(eosio::name from, eosio::name to, eosio::name category, eosio::name token_name, eosio::asset quantity, string memo)

Transfer the fungible tokens category:token_name. Only applicable if the token is transferable. The quantity must match the symbol and precision of max_supply.

ACTION transfernft(eosio::name from, eosio::name to, vector<uint64_t> dgood_ids, string memo)

Transfer non-fungible tokens. Only applicable if the token is transferable and not be locked (see table lockednfts). dgood_ids are from table dgood.

ACTION burnft(eosio::name owner, uint64_t category_name_id, eosio::asset quantity)

Destroys fungible tokens and frees the RAM if all tokens are deleted from the account. Only applicable if the token is burnable. Only the owner may call this action. The quantity must match the symbol and precision of max_supply. The category_name_id is from table dgoodstats.

ACTION burnnft(eosio::name owner, vector<uint64_t> dgood_ids)

Destroys specified non-fungible tokens and frees the RAM. Only applicable if the token is burnable and not be locked (see table lockednfts). Only the owner may call this action. dgood_ids are from table dgood.

ACTION pausexfer(bool pause)

Pauses all transfers of all tokens. Only callable by the contract. If pause is true, will pause. If pause is false will unpause transfers.