ERC-721

什么是 ERC-721?

ERC-721 是一个描述了如何在以太坊区块链上构建不可替代的或者唯一的代币的自由开放的标准。相对于多数代币都是可互相替代的(每个代币都与其他代币相同),ERC-721 代币则是独一无二的。

请把它们当成独一无二的稀有收藏品。

ERC-20:一种同质代币

ERC-721:一种非同质代币

标准

ERC-721 定义了一个智能合约需要实现最小的接口集,允许对唯一的代币进行管理、持有和交易。它不强制规定代币元数据的标准,也不限制在此上添加的附加功能。

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/*
* @title ERC721 接口
*/

contract ERC721 {
/// @dev This emits when ownership of any NFT changes by any mechanism.
/// This event emits when NFTs are created (`from` == 0) and destroyed
/// (`to` == 0). Exception: during contract creation, any number of NFTs
/// may be created and assigned without emitting Transfer. At the time of
/// any transfer, the approved address for that NFT (if any) is reset to none.
event Transfer(address indexed _from, address indexed _to, uint256 _tokenId);

/// @dev This emits when the approved address for an NFT is changed or
/// reaffirmed. The zero address indicates there is no approved address.
/// When a Transfer event emits, this also indicates that the approved
/// address for that NFT (if any) is reset to none.
event Approval(address indexed _owner, address indexed _approved, uint256 _tokenId);

/// @dev This emits when an operator is enabled or disabled for an owner.
/// The operator can manage all NFTs of the owner.
event ApprovalForAll(address indexed _owner, address indexed _operator, bool _approved);

/// @notice Count all NFTs assigned to an owner
/// @dev NFTs assigned to the zero address are considered invalid, and this
/// function throws for queries about the zero address.
/// @param _owner An address for whom to query the balance
/// @return The number of NFTs owned by `_owner`, possibly zero
function balanceOf(address _owner) external view returns (uint256);

/// @notice Find the owner of an NFT
/// @param _tokenId The identifier for an NFT
/// @dev NFTs assigned to zero address are considered invalid, and queries
/// about them do throw.
/// @return The address of the owner of the NFT
function ownerOf(uint256 _tokenId) external view returns (address);

/// @notice Transfers the ownership of an NFT from one address to another address
/// @dev Throws unless `msg.sender` is the current owner, an authorized
/// operator, or the approved address for this NFT. Throws if `_from` is
/// not the current owner. Throws if `_to` is the zero address. Throws if
/// `_tokenId` is not a valid NFT. When transfer is complete, this function
/// checks if `_to` is a smart contract (code size > 0). If so, it calls
/// `onERC721Received` on `_to` and throws if the return value is not
/// `bytes4(keccak256("onERC721Received(address,uint256,bytes)"))`.
/// @param _from The current owner of the NFT
/// @param _to The new owner
/// @param _tokenId The NFT to transfer
/// @param data Additional data with no specified format, sent in call to `_to`
function safeTransferFrom(address _from, address _to, uint256 _tokenId, bytes data) external payable;

/// @notice Transfers the ownership of an NFT from one address to another address
/// @dev This works identically to the other function with an extra data parameter,
/// except this function just sets data to ""
/// @param _from The current owner of the NFT
/// @param _to The new owner
/// @param _tokenId The NFT to transfer
function safeTransferFrom(address _from, address _to, uint256 _tokenId) external payable;

/// @notice Transfer ownership of an NFT -- THE CALLER IS RESPONSIBLE
/// TO CONFIRM THAT `_to` IS CAPABLE OF RECEIVING NFTS OR ELSE
/// THEY MAY BE PERMANENTLY LOST
/// @dev Throws unless `msg.sender` is the current owner, an authorized
/// operator, or the approved address for this NFT. Throws if `_from` is
/// not the current owner. Throws if `_to` is the zero address. Throws if
/// `_tokenId` is not a valid NFT.
/// @param _from The current owner of the NFT
/// @param _to The new owner
/// @param _tokenId The NFT to transfer
function transferFrom(address _from, address _to, uint256 _tokenId) external payable;

/// @notice Set or reaffirm the approved address for an NFT
/// @dev The zero address indicates there is no approved address.
/// @dev Throws unless `msg.sender` is the current NFT owner, or an authorized
/// operator of the current owner.
/// @param _approved The new approved NFT controller
/// @param _tokenId The NFT to approve
function approve(address _approved, uint256 _tokenId) external payable;

/// @notice Enable or disable approval for a third party ("operator") to manage
/// all of `msg.sender`'s assets.
/// @dev Emits the ApprovalForAll event
/// @param _operator Address to add to the set of authorized operators.
/// @param _approved True if the operators is approved, false to revoke approval
function setApprovalForAll(address _operator, bool _approved) external;

/// @notice Get the approved address for a single NFT
/// @dev Throws if `_tokenId` is not a valid NFT
/// @param _tokenId The NFT to find the approved address for
/// @return The approved address for this NFT, or the zero address if there is none
function getApproved(uint256 _tokenId) external view returns (address);

/// @notice Query if an address is an authorized operator for another address
/// @param _owner The address that owns the NFTs
/// @param _operator The address that acts on behalf of the owner
/// @return True if `_operator` is an approved operator for `_owner`, false otherwise
function isApprovedForAll(address _owner, address _operator) external view returns (bool);

/// @notice Query if a contract implements an interface
/// @param interfaceID The interface identifier, as specified in ERC-165
/// @dev Interface identification is specified in ERC-165. This function
/// uses less than 30,000 gas.
/// @return `true` if the contract implements `interfaceID` and
/// `interfaceID` is not 0xffffffff, `false` otherwise
function supportsInterface(bytes4 interfaceID) external view returns (bool);
}

ERC-721 标准是由 @dete 提出的 EIP 草案,并由 Axiom Zen 首次在加密猫项目上落地。

ERC-721 已经脱离测试版并进入社区规范 v1,支持和支持了大量加密生态系统的项目。如果脱离社区成员的奉献,该 EIP 是不能实现的。特别感谢 @fulldecent 和其他为推动这一进步付出大量努力的人们。

ERC-721 测试时期构建的项目

  • CryptoCelebrities
  • CryptoKitties
  • EtherTulips

构建你自己的 ERC-721 代币

交易 ERC-721 代币

参考资料