ERC721 示例
pragma solidity ^0.8.6;
interface IERC165 {
function supportsInterface(bytes4 interfaceID) external view returns (bool);
}
interface IERC721 is IERC165 {
function balanceOf(address owner) external view returns (uint balance);
function ownerOf(uint tokenId) external view returns (address owner);
function safeTransferFrom(
address from,
address to,
uint tokenId
) external;
function safeTransferFrom(
address from,
address to,
uint tokenId,
bytes calldata data
) external;
function transferFrom(
address from,
address to,
uint tokenId
) external;
function approve(address to, uint tokenId) external;
function getApproved(uint tokenId) external view returns (address operator);
function setApprovalForAll(address operator, bool _approved) external;
function isApprovedForAll(address owner, address operator)
external
view
returns (bool);
}
interface IERC721Receiver {
function onERC721Received(
address operator,
address from,
uint tokenId,
bytes calldata data
) external returns (bytes4);
}
contract ERC721 is IERC721 {
using Address for address;
event Transfer(address indexed from, address indexed to, uint indexed tokenId);
event Approval(
address indexed owner,
address indexed approved,
uint indexed tokenId
);
event ApprovalForAll(
address indexed owner,
address indexed operator,
bool approved
);
mapping(uint => address) private _owners;
mapping(address => uint) private _balances;
mapping(uint => address) private _tokenApprovals;
mapping(address => mapping(address => bool)) private _operatorApprovals;
function supportsInterface(bytes4 interfaceId)
external
pure
override
returns (bool)
{
return
interfaceId == type(IERC721).interfaceId ||
interfaceId == type(IERC165).interfaceId;
}
function balanceOf(address owner) external view override returns (uint) {
require(owner != address(0), "owner = zero address");
return _balances[owner];
}
function ownerOf(uint tokenId) public view override returns (address owner) {
owner = _owners[tokenId];
require(owner != address(0), "token doesn't exist");
}
function isApprovedForAll(address owner, address operator)
external
view
override
returns (bool)
{
return _operatorApprovals[owner][operator];
}
function setApprovalForAll(address operator, bool approved) external override {
_operatorApprovals[msg.sender][operator] = approved;
emit ApprovalForAll(msg.sender, operator, approved);
}
function getApproved(uint tokenId) external view override returns (address) {
require(_owners[tokenId] != address(0), "token doesn't exist");
return _tokenApprovals[tokenId];
}
function _approve(
address owner,
address to,
uint tokenId
) private {
_tokenApprovals[tokenId] = to;
emit Approval(owner, to, tokenId);
}
function approve(address to, uint tokenId) external override {
address owner = _owners[tokenId];
require(
msg.sender == owner || _operatorApprovals[owner][msg.sender],
"not owner nor approved for all"
);
_approve(owner, to, tokenId);
}
function _isApprovedOrOwner(
address owner,
address spender,
uint tokenId
) private view returns (bool) {
return (spender == owner ||
_tokenApprovals[tokenId] == spender ||
_operatorApprovals[owner][spender]);
}
function _transfer(
address owner,
address from,
address to,
uint tokenId
) private {
require(from == owner, "not owner");
require(to != address(0), "transfer to the zero address");
_approve(owner, address(0), tokenId);
_balances[from] -= 1;
_balances[to] += 1;
_owners[tokenId] = to;
emit Transfer(from, to, tokenId);
}
function transferFrom(
address from,
address to,
uint tokenId
) external override {
address owner = ownerOf(tokenId);
require(
_isApprovedOrOwner(owner, msg.sender, tokenId),
"not owner nor approved"
);
_transfer(owner, from, to, tokenId);
}
function _checkOnERC721Received(
address from,
address to,
uint tokenId,
bytes memory _data
) private returns (bool) {
if (to.isContract()) {
return
IERC721Receiver(to).onERC721Received(
msg.sender,
from,
tokenId,
_data
) == IERC721Receiver.onERC721Received.selector;
} else {
return true;
}
}
function _safeTransfer(
address owner,
address from,
address to,
uint tokenId,
bytes memory _data
) private {
_transfer(owner, from, to, tokenId);
require(_checkOnERC721Received(from, to, tokenId, _data), "not ERC721Receiver");
}
function safeTransferFrom(
address from,
address to,
uint tokenId,
bytes memory _data
) public override {
address owner = ownerOf(tokenId);
require(
_isApprovedOrOwner(owner, msg.sender, tokenId),
"not owner nor approved"
);
_safeTransfer(owner, from, to, tokenId, _data);
}
function safeTransferFrom(
address from,
address to,
uint tokenId
) external override {
safeTransferFrom(from, to, tokenId, "");
}
function mint(address to, uint tokenId) external {
require(to != address(0), "mint to zero address");
require(_owners[tokenId] == address(0), "token already minted");
_balances[to] += 1;
_owners[tokenId] = to;
emit Transfer(address(0), to, tokenId);
}
function burn(uint tokenId) external {
address owner = ownerOf(tokenId);
require(msg.sender == owner, "not owner of token");
_approve(owner, address(0), tokenId);
_balances[owner] -= 1;
delete _owners[tokenId];
emit Transfer(owner, address(0), tokenId);
}
}
library Address {
function isContract(address account) internal view returns (bool) {
uint size;
assembly {
size := extcodesize(account)
}
return size > 0;
}
}
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