ERC1155Supply

ERC1155Supply

Git Source

Inherits: ERC1155

Extension of ERC1155 that adds tracking of total supply per id. Useful for scenarios where Fungible and Non-fungible tokens have to be clearly identified. Note: While a totalSupply of 1 might mean the corresponding is an NFT, there is no guarantees that no other token with the same id are not going to be minted.

State Variables

_totalSupply

keeps track of per-token id's total supply, as well as overall supply. also used as a counter when minting, by reading the .length property of the array.

uint256[] internal _totalSupply;

Functions

totalSupply

Returns the total supply of a specific token ID.

The total value transferred from address 0x0 minus the total value transferred to 0x0 observed via the TransferSingle and TransferBatch events MAY be used by clients and exchanges to determine the “circulating supply” for a given token ID.

function totalSupply(uint256 _id) public view returns (uint256);

Parameters

Name	Type	Description
_id	uint256	The token ID to query.

Returns

Name	Type	Description
<none>	uint256	The total supply of the token.

totalSupply

Returns the total number of unique token IDs in this collection.

Required in order to enumerate _totalSupply (or _tokenURIs, see ERC1155Metadata_URI-uri) from a client.

function totalSupply() public view returns (uint256);

Returns

Name	Type	Description
<none>	uint256	The total number of unique token IDs.

exists

Checks if a token exists with a given ID.

Note that for implementations such as open editions, token IDs with a supply of 0 may exist, i.e. minting with 0 supply may be intentional. Tokens can be managed by their owner or approved accounts via {approve} or {setApprovalForAll}. Tokens start existing when they are minted (_mint), and stop existing when they are burned (_burn).

function exists(uint256 _id) public view returns (bool);

Parameters

Name	Type	Description
_id	uint256	The token ID to check.

Returns

Name	Type	Description
<none>	bool	True if the token exists, false otherwise.

_mint

Mints a new token.

Because _mint is never (and MUST not be) invoked in order to mint additional supply for an existing tokenId, it is more efficient to push a new element into the array rather than writing to an arbitrary index such as _totalSupply[_id] += _totalSupply. For this reason it was named more aptly _totalSupply, rather than _value.

function _mint(address _to, uint256 _id, uint256 totalSupply_, bytes memory _data) internal virtual override;

Parameters

Name	Type	Description
_to	address	The address to mint the token to.
_id	uint256	The token ID; the child/derived contract is responsible for calculating it.
totalSupply_	uint256	The total supply for the new token.
_data	bytes	The data to associate with the token.

_burn

Burns a specific token.

totalSupply MUST be incremented before transfering the control flow to _mint, which could include external calls, which could result in reentrancy. E.g. https://medium.com/chainsecurity/totalsupply-inconsistency-in-erc1155-nft-tokens-8f8e3b29f5aa

Since _balanceOf has been decremented by the base contract _burn function by calling super._burn first, and since the sum of balances can never exceed totalSupply, we can safely decrement totalSupply without requiring to check for underflow. Since there are no external calls being made in _burn, there is no risk of reentrancy that could exploit _totalSupply.

function _burn(address _from, uint256 _id, uint256 _value) internal virtual override;

Parameters

Name	Type	Description
_from	address	The owner of the token.
_id	uint256	The token ID to burn.
_value	uint256	The amount of tokens to burn.