The standard introduces a in which each issued token is unique and distinct from others. This standard defines functions and events that enable the creation, ownership, and transfer of non-fungible assets.
Note:ERC-721 Token addresses refer to full Hedera Token Service (HTS) fungible token entities. These tokens can be fully managed by HTS API calls. Additionally, by utilizing interfaces or system contract functions, these tokens can also be managed by smart contracts on Hedera.
Supported Functions
From Interface ERC-721
ownerOf
Returns the account ID of the specified HTS token owner. The _tokenId is the Hedera serial number of the NFT.
approve
Gives the spender permission to transfer a token (_tokenId) to another account from the owner. The approval is cleared when the token is transferred. The _tokenId is the Hedera serial number of the NFT.
This works by creating a synthetic CryptoApproveAllowanceTransaction with payer - the account that called the precompile (the message sender property of the message frame in the EVM).
If the spender address is 0, this creates a CryptoDeleteAllowanceTransaction instead and removes any allowances previously approved on the token.
Fires an approval event with the following signature when executed:
function setApprovalForAll(address _operator, bool _approved) external
Approve or remove an operator as an operator for the caller. Operators can call transferFrom for any token owned by the caller.
This works by creating a synthetic CryptoApproveAllowanceTransaction with payer - the account that called the precompile (the message sender property of the message frame in the EVM).
getApproved
function getApproved(uint256 _tokenId) external view returns (address)
Returns the account approved for the specified _tokenId. The _tokenId is the Hedera serial number of the NFT.
This works by loading the SPENDER property of the token from the NFTs ledger.
isApprovedForAll
function isApprovedForAll(address _owner, address _operator) external view returns (bool)
Returns if the operator is allowed to manage all of the assets of owner.
This works by loading the APPROVE_FOR_ALL_NFTS_ALLOWANCES property of the owner account and verifying if the list of approved for all accounts contains the account id of the operator.
transferFrom
Transfers a token (_tokenId) from a Hedera account (from) to another Hedera account (to) in Solidity format. The _tokenId is the Hedera serial number of the NFT.
This works by creating a synthetic CryptoTransferTransaction with nft token transfers with the is_approval property set to true.
From Interface ERC721Metadata
name
Returns the name of the HTS non-fungible token.
symbol
Returns the symbol of the HTS non-fungible token.
tokenURI
Returns the token metadata of the HTS non-fungible token. This corresponds to the NFT metadata field when minting an NFT using HTS. The _tokenId is the Hedera serial number of the NFT.
From Interface ERC721Enumerable
totalSupply
Returns the total supply of the HTS non-fungible token.
Unsupported Functions
The following ERC-721 operations will not be natively supported on Hedera and will return a failure if they're called. Advanced functionality is achievable only through custom implementations within smart contracts.
From interface ERC-721
safeTransferFrom
From interface ERC721Enumerable
tokenByIndex
tokenOfOwnerByIndex
All semantics of Interface ERC721TokenReceiver
Existing Hedera token association rules will take the place of such checks.
Additional References
function transferFrom(address _from, address _to, uint256 _tokenId) external payable
function name() external view returns (string _name)
function symbol() external view returns (string _symbol)
function tokenURI(uint256 _tokenId) external view returns (string)
function totalSupply() external view returns (uint256)
function safeTransferFrom(address token, address from, address to, uint256 tokenId)
function tokenByIndex(uint256 _index) external view returns (uint256)
function tokenOfOwnerByIndex(address _owner, uint256 _index) external view returns (uint256)
