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Update transfer naming and interface IDs
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William Entriken
GitHub
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89d0162231
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2bddd126de
@ -46,8 +46,8 @@ pragma solidity ^0.4.20;
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/// @title ERC-721 Non-Fungible Token Standard
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/// @dev See https://github.com/ethereum/EIPs/blob/master/EIPS/eip-721.md
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/// Note: the ERC-165 identifier for this interface is 0xTODO_FILL_IN
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interface ERC721 /* is ERC165 */ {
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/// Note: the ERC-165 identifier for this interface is 0x6466353c
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interface ERC721 /* is ERC165 */ {
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/// @dev This emits when ownership of any NFT changes by any mechanism.
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/// This event emits when NFTs are created (`from` == 0) and destroyed
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/// (`to` == 0). Exception: during contract creation, any number of NFTs
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@ -79,6 +79,28 @@ interface ERC721 /* is ERC165 */ {
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/// @return The address of the owner of the NFT
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function ownerOf(uint256 _tokenId) external view returns (address);
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/// @notice Transfers the ownership of an NFT from one address to another address
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/// @dev Throws unless `msg.sender` is the current owner, an authorized
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/// operator, or the approved address for this NFT. Throws if `_from` is
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/// not the current owner. Throws if `_to` is the zero address. Throws if
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/// `_tokenId` is not a valid NFT. When transfer is complete, this function
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/// checks if `_to` is a smart contract (code size > 0). If so, it calls
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/// `onERC721Received` on `_to` and throws if the return value is not
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/// `bytes4(keccak256("onERC721Received(address,uint256,bytes)"))`.
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/// @param _from The current owner of the NFT
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/// @param _to The new owner
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/// @param _tokenId The NFT to transfer
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/// @param data Additional data with no specified format, sent in call to `_to`
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function safeTransferFrom(address _from, address _to, uint256 _tokenId, bytes data) external payable;
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/// @notice Transfers the ownership of an NFT from one address to another address
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/// @dev This works identically to the other function with an extra data parameter,
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/// except this function just sets data to []
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/// @param _from The current owner of the NFT
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/// @param _to The new owner
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/// @param _tokenId The NFT to transfer
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function safeTransferFrom(address _from, address _to, uint256 _tokenId) external payable;
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/// @notice Transfer ownership of an NFT -- THE CALLER IS RESPONSIBLE
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/// TO CONFIRM THAT `_to` IS CAPABLE OF RECEIVING NFTS OR ELSE
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/// THEY MAY BE PERMANENTLY LOST
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@ -89,28 +111,6 @@ interface ERC721 /* is ERC165 */ {
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/// @param _from The current owner of the NFT
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/// @param _to The new owner
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/// @param _tokenId The NFT to transfer
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function unsafeTransfer(address _from, address _to, uint256 _tokenId) external payable;
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/// @notice Transfers the ownership of an NFT from one address to another address
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/// @dev Throws unless `msg.sender` is the current owner, an authorized
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/// operator, or the approved address for this NFT. Throws if `_from` is
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/// not the current owner. Throws if `_to` is the zero address. Throws if
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/// `_tokenId` is not a valid NFT. When transfer is complete, this function
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/// checks if `_to` is a smart contract (code size > 0). If so, it calls
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/// `onNFTReceived` on `_to` and throws if the return value is not
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/// `bytes4(keccak256("onNFTReceived(address,uint256,bytes)"))`.
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/// @param _from The current owner of the NFT
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/// @param _to The new owner
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/// @param _tokenId The NFT to transfer
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/// @param data Additional data with no specified format, sent in call to `_to`
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function transferFrom(address _from, address _to, uint256 _tokenId, bytes data) external payable;
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/// @notice Transfers the ownership of an NFT from one address to another address
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/// @dev This works identically to the other function with an extra data parameter,
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/// except this function just sets data to []
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/// @param _from The current owner of the NFT
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/// @param _to The new owner
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/// @param _tokenId The NFT to transfer
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function transferFrom(address _from, address _to, uint256 _tokenId) external payable;
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/// @notice Set or reaffirm the approved address for an NFT
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@ -132,13 +132,13 @@ interface ERC721 /* is ERC165 */ {
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/// @dev Throws if `_tokenId` is not a valid NFT
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/// @param _tokenId The NFT to find the approved address for
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/// @return The approved address for this NFT, or the zero address if there is none
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function getApproved(uint256 _tokenId) returns (address);
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function getApproved(uint256 _tokenId) external returns (address);
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/// @notice Query if an address is an authorized operator for another address
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/// @param _owner The address that owns the NFTs
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/// @param _operator The address that acts on behalf of the owner
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/// @return True if `_operator` is an approved operator for `_owner`, false otherwise
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function isApprovedForAll(address _owner, address _operator) returns (bool);
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function isApprovedForAll(address _owner, address _operator) external view returns (bool);
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}
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interface ERC165 {
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@ -155,6 +155,7 @@ interface ERC165 {
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A wallet/broker/auction application MUST implement the **wallet interface** if it will accept safe transfers.
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```solidity
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/// @dev Note: the ERC-165 identifier for this interface is 0xf0b9e5ba
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interface ERC721TokenReceiver {
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/// @notice Handle the receipt of an NFT
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/// @dev The ERC721 smart contract calls this function on the recipient
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@ -165,8 +166,9 @@ interface ERC721TokenReceiver {
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/// @param _from The sending address
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/// @param _tokenId The NFT identifier which is being transfered
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/// @param data Additional data with no specified format
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/// @return Always returns `keccak256("ERC721_ONNFTRECEIVED")`, unless throwing
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function onNFTReceived(address _from, uint256 _tokenId, bytes data) external returns(bytes4);
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/// @return `bytes4(keccak256("onERC721Received(address,uint256,bytes)"))`
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/// unless throwing
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function onERC721Received(address _from, uint256 _tokenId, bytes data) external returns(bytes4);
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}
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```
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@ -175,7 +177,7 @@ The **metadata extension** is OPTIONAL for ERC-721 smart contracts (see "caveats
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```solidity
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/// @title ERC-721 Non-Fungible Token Standard, optional metadata extension
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/// @dev See https://github.com/ethereum/EIPs/blob/master/EIPS/eip-721.md
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/// Note: the ERC-165 identifier for this interface is 0xTODO_ADD_THIS
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/// Note: the ERC-165 identifier for this interface is 0x5b5e139f
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interface ERC721Metadata /* is ERC721 */ {
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/// @notice A descriptive name for a collection of NFTs in this contract
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function name() external pure returns (string _name);
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@ -219,7 +221,7 @@ The **enumeration extension** is OPTIONAL for ERC-721 smart contracts (see "cave
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```solidity
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/// @title ERC-721 Non-Fungible Token Standard, optional enumeration extension
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/// @dev See https://github.com/ethereum/EIPs/blob/master/EIPS/eip-721.md
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/// Note: the ERC-165 identifier for this interface is 0xTODO_ADD_THIS
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/// Note: the ERC-165 identifier for this interface is 0x780e9d63
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interface ERC721Enumerable /* is ERC721 */ {
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/// @notice Count NFTs tracked by this contract
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/// @return A count of valid NFTs tracked by this contract, where each one of
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@ -233,16 +235,6 @@ interface ERC721Enumerable /* is ERC721 */ {
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/// (sort order not specified)
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function tokenByIndex(uint256 _index) external view returns (uint256);
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/// @notice Count of owners which own at least one NFT
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/// @return A count of the number of owners which own NFTs
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function countOfOwners() external view returns (uint256);
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/// @notice Enumerate owners which own at least one NFT
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/// @dev Throws if `_index` >= `countOfOwners()`
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/// @param _index A counter less than `countOfOwners()`
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/// @return The address of the `_index`th owner (sort order not specified)
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function ownerByIndex(uint256 _index) external view returns (address);
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/// @notice Enumerate NFTs assigned to an owner
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/// @dev Throws if `_index` >= `balanceOf(_owner)` or if
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/// `_owner` is the zero address, representing invalid NFTs.
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@ -283,7 +275,7 @@ The choice of `uint256` allows a wide variety of applications because UUIDs and
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**Transfer mechanism**
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ERC-721 standardizes a safe transfer function `transferFrom` (overloaded with and without a `bytes` parameter) and an unsafe function `unsafeTransfer`. Transfers may be initiated by:
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ERC-721 standardizes a safe transfer function `safeTransferFrom` (overloaded with and without a `bytes` parameter) and an unsafe function `transferFrom`. Transfers may be initiated by:
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- The owner of an NFT
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- The approved address of an NFT
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@ -291,19 +283,19 @@ ERC-721 standardizes a safe transfer function `transferFrom` (overloaded with an
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Additionally, an authorized operator may set the approved address for an NFT. This provides a powerful set of tools for wallet, broker and auction applications to quickly use a *large* number of NFTs.
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The transfer and accept functions documentation only specify conditions when the transaction MUST throw. Your implementation MAY also throw in other situations. This allows implementations to achieve interesting results:
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The transfer and accept functions' documentation only specify conditions when the transaction MUST throw. Your implementation MAY also throw in other situations. This allows implementations to achieve interesting results:
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- **Disallow transfers if the contract is paused** — prior art, [Crypto Kitties](https://github.com/axiomzen/cryptokitties-bounty/blob/master/contracts/KittyOwnership.sol#L79)
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- **Blacklist certain address from receiving deeds** — prior art, [Crypto Kitties, (lines 565, 566)](https://etherscan.io/address/0x06012c8cf97bead5deae237070f9587f8e7a266d#code).
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- **Disallow unsafe transfers** — `unsafeTransfer` throws unless `_to` equals `msg.sender` or `countOf(_to)` is non-zero (because such cases are safe)
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- **Charge a fee to both parties of a transaction** — require payment when calling `approve` with a non-zero `_approved` if it was previously the zero address, refund payment if calling `approve` with the zero address if it was previously a non-zero address, require payment when calling `transfer`, require `transfer` parameter `_to` to equal `msg.sender`, require `transfer` parameter `_to` to be the approved address for the deed
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- **Read only deed registry** — always throw from `unsafeTransfer`, `transferFrom`, `approve` and `setApprovalForAll`
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- **Blacklist certain address from receiving NFTs** — prior art, [Crypto Kitties, (lines 565, 566)](https://etherscan.io/address/0x06012c8cf97bead5deae237070f9587f8e7a266d#code).
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- **Disallow unsafe transfers** — `transferFrom` throws unless `_to` equals `msg.sender` or `countOf(_to)` is non-zero or was non-zero previously (because such cases are safe)
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- **Charge a fee to both parties of a transaction** — require payment when calling `approve` with a non-zero `_approved` if it was previously the zero address, refund payment if calling `approve` with the zero address if it was previously a non-zero address, require payment when calling any transfer function, require transfer parameter `_to` to equal `msg.sender`, require transfer parameter `_to` to be the approved address for the NFT
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- **Read only NFT registry** — always throw from `unsafeTransfer`, `transferFrom`, `approve` and `setApprovalForAll`
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Failed transactions will throw, a best practice identified in [ERC-233](https://github.com/ethereum/EIPs/issues/223) , [ERC-677](https://github.com/ethereum/EIPs/issues/677), [ERC-827](https://github.com/ethereum/EIPs/issues/827) and [OpenZeppelin](https://github.com/OpenZeppelin/zeppelin-solidity/blob/master/contracts/token/ERC20/SafeERC20.sol). [ERC-20](https://github.com/ethereum/EIPs/blob/master/EIPS/eip-20-token-standard.md) defined an `allowance` feature, this caused a problem when called and then later modified to a different amount, as [disucssed on OpenZeppelin](https://github.com/OpenZeppelin/zeppelin-solidity/issues/438). In ERC-721, there is no allowance because every deed is unique, the quantity is none or one. Therefore we receive the benefits of ERC-20's original design without problems that have been later discovered.
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Failed transactions will throw, a best practice identified in [ERC-233](https://github.com/ethereum/EIPs/issues/223) , [ERC-677](https://github.com/ethereum/EIPs/issues/677), [ERC-827](https://github.com/ethereum/EIPs/issues/827) and [OpenZeppelin](https://github.com/OpenZeppelin/zeppelin-solidity/blob/master/contracts/token/ERC20/SafeERC20.sol). [ERC-20](https://github.com/ethereum/EIPs/blob/master/EIPS/eip-20-token-standard.md) defined an `allowance` feature, this caused a problem when called and then later modified to a different amount, as [disucssed on OpenZeppelin](https://github.com/OpenZeppelin/zeppelin-solidity/issues/438). In ERC-721, there is no allowance because every NFT is unique, the quantity is none or one. Therefore we receive the benefits of ERC-20's original design without problems that have been later discovered.
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Creating of NFTs ("minting") and destruction NFTs ("burning") is not included in the specification. Your contract may implement these by other means. Please see the `event` documentation for your responsibilities when creating or destroying NFTs.
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*Alternatives considered: only allow two-step ERC-20 style transaction, require that `transfer` never throw, require all functions to return a boolean indicating the success of the operation.*
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*Alternatives considered: only allow two-step ERC-20 style transaction, require that transfer functions never throw, require all functions to return a boolean indicating the success of the operation.*
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**ERC-165 interface**
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@ -358,7 +350,7 @@ We have been very inclusive in this process and invite anyone with questions or
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We have adopted `balanceOf`, `totalSupply`, `name` and `symbol` semantics from the [ERC-20](https://github.com/ethereum/EIPs/blob/master/EIPS/eip-20.md) specification. An implementation may also include a function `decimals` that returns `uint8(0)` if its goal is to be more compatible with ERC-20 while supporting this standard. However, we find it contrived to require all ERC-721 implementations to support the `decimals` function.
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Example DAR implementations as of February 2018:
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Example NFT implementations as of February 2018:
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- [CryptoKitties](https://www.cryptokitties.co/) — Compatible with an earlier version of this standard.
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- [CryptoPunks](https://www.larvalabs.com/cryptopunks) — Partially ERC-20 compatible, but not easily generalizable because it includes auction functionality directly in the contract and uses function names that explicitly refer to the assets as "punks".
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@ -366,7 +358,7 @@ Example DAR implementations as of February 2018:
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Note: "Limited edition, collectible tokens" like [Curio Cards](https://mycuriocards.com/) and [Rare Pepe](https://rarepepewallet.com/) are *not* distinguishable assets. They're actually a collection of individual fungible tokens, each of which is tracked by its own smart contract with its own total supply (which may be `1` in extreme cases).
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The `onNFTReceived` function specifically works around old deployed contracts [which may inadvertently return 1 (`true`)](http://solidity.readthedocs.io/en/develop/bugs.html#DelegateCallReturnValue) in certain circumstances even if they don't implement a function. By returning, and checking for, a magic value we are able to distinguish actual affirmative responses versus these `true`s.
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The `onERC721Received` function specifically works around old deployed contracts [which may inadvertently return 1 (`true`)](http://solidity.readthedocs.io/en/develop/bugs.html#DelegateCallReturnValue) in certain circumstances even if they don't implement a function. By returning, and checking for, a magic value we are able to distinguish actual affirmative responses versus these `true`s.
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## Test Cases
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