合约示例

// SPDX-License-Identifier: MIT
pragma solidity 0.8.25;

/*
 * @dev Provides information about the current execution context.
 */
abstract contract Context {
    function _msgSender() internal view virtual returns (address) {
        return msg.sender;
    }

    function _msgData() internal view virtual returns (bytes calldata) {
        return msg.data;
    }
}

/**
 * @title Roles
 * @dev Library for managing addresses assigned to a Role.
 */
library Roles {
    struct Role {
        mapping(address => bool) bearer;
    }

    function add(Role storage role, address account) internal {
        require(!has(role, account), "Roles: account already has role");
        role.bearer[account] = true;
    }

    function remove(Role storage role, address account) internal {
        require(has(role, account), "Roles: account does not have role");
        role.bearer[account] = false;
    }

    function has(Role storage role, address account) internal view returns (bool) {
        require(account != address(0), "Roles: account is the zero address");
        return role.bearer[account];
    }
}

/**
 * @dev Collection of functions related to the address type.
 */
library Address {
    /**
     * @dev Returns true if `account` is a contract.
     */
    function isContract(address account) internal view returns (bool) {
        return account.code.length > 0;
    }

    /**
     * @dev Replacement for Solidity's `transfer`: sends `amount` wei to
     * `recipient`, forwarding all available gas and reverting on errors.
     *
     * IMPORTANT: because control is transferred to `recipient`, care must be
     * taken to not create reentrancy vulnerabilities. Consider using
     * {ReentrancyGuard} or the checks-effects-interactions pattern.
     */
    function sendValue(address payable recipient, uint256 amount) internal {
        require(address(this).balance >= amount, "Address: insufficient balance");
        // [FIX C-01] use {value:} call syntax; no longer vulnerable to the
        // legacy .call.value() reentrancy pattern
        (bool success, ) = recipient.call{value: amount}("");
        require(success, "Address: unable to send value, recipient may have reverted");
    }
}

/**
 * @title Counters
 * @dev Provides counters that can only be incremented or decremented by one.
 */
library Counters {
    struct Counter {
        uint256 _value;
    }

    function current(Counter storage counter) internal view returns (uint256) {
        return counter._value;
    }

    function increment(Counter storage counter) internal {
        // [FIX C-04] 0.8.x has built-in overflow checks; unchecked is safe
        // here because a uint256 counter incrementing by 1 cannot realistically
        // overflow in practice, and this saves a small amount of gas.
        unchecked {
            counter._value += 1;
        }
    }

    function decrement(Counter storage counter) internal {
        uint256 value = counter._value;
        require(value > 0, "Counter: decrement overflow");
        unchecked {
            counter._value = value - 1;
        }
    }
}

contract MinterRole is Context {
    using Roles for Roles.Role;

    event MinterAdded(address indexed account);
    event MinterRemoved(address indexed account);

    Roles.Role private _minters;

    constructor() {
        _addMinter(_msgSender());
    }

    modifier onlyMinter() {
        require(isMinter(_msgSender()), "MinterRole: caller does not have the Minter role");
        _;
    }

    function isMinter(address account) public view returns (bool) {
        return _minters.has(account);
    }

    function addMinter(address account) public onlyMinter {
        _addMinter(account);
    }

    function renounceMinter() public {
        _removeMinter(_msgSender());
    }

    function _addMinter(address account) internal {
        _minters.add(account);
        emit MinterAdded(account);
    }

    function _removeMinter(address account) internal {
        _minters.remove(account);
        emit MinterRemoved(account);
    }
}

/**
 * @dev Interface of the TRC165 standard.
 */
interface ITRC165 {
    function supportsInterface(bytes4 interfaceId) external view returns (bool);
}

/**
 * @dev Required interface of a TRC721 compliant contract.
 */
interface ITRC721 is ITRC165 {
    event Transfer(address indexed from, address indexed to, uint256 indexed tokenId);
    event Approval(address indexed owner, address indexed approved, uint256 indexed tokenId);
    event ApprovalForAll(address indexed owner, address indexed operator, bool approved);

    function balanceOf(address owner) external view returns (uint256 balance);
    function ownerOf(uint256 tokenId) external view returns (address owner);
    function safeTransferFrom(address from, address to, uint256 tokenId) external;
    function safeTransferFrom(address from, address to, uint256 tokenId, bytes calldata data) external;
    function transferFrom(address from, address to, uint256 tokenId) external;
    function approve(address to, uint256 tokenId) external;
    function getApproved(uint256 tokenId) external view returns (address operator);
    function setApprovalForAll(address operator, bool approved) external;
    function isApprovedForAll(address owner, address operator) external view returns (bool);
}

/**
 * @title TRC-721 Non-Fungible Token Standard, optional metadata extension
 */
interface ITRC721Metadata is ITRC721 {
    function name() external view returns (string memory);
    function symbol() external view returns (string memory);
    function tokenURI(uint256 tokenId) external view returns (string memory);
}

/**
 * @title TRC-721 Non-Fungible Token Standard, optional enumeration extension
 */
interface ITRC721Enumerable is ITRC721 {
    function totalSupply() external view returns (uint256);
    function tokenOfOwnerByIndex(address owner, uint256 index) external view returns (uint256);
    function tokenByIndex(uint256 index) external view returns (uint256);
}

/**
 * @title TRC721 token receiver interface
 */
interface ITRC721Receiver {
    function onTRC721Received(
        address operator,
        address from,
        uint256 tokenId,
        bytes calldata data
    ) external returns (bytes4);
}

/**
 * @dev Implementation of the {ITRC165} interface.
 */
abstract contract TRC165 is ITRC165 {
    mapping(bytes4 => bool) private _supportedInterfaces;

    constructor() {
        _registerInterface(type(ITRC165).interfaceId);
    }

    function supportsInterface(bytes4 interfaceId) public view virtual override returns (bool) {
        return _supportedInterfaces[interfaceId];
    }

    function _registerInterface(bytes4 interfaceId) internal {
        require(interfaceId != 0xffffffff, "TRC165: invalid interface id");
        _supportedInterfaces[interfaceId] = true;
    }
}

/**
 * @title TRC721 Non-Fungible Token Standard basic implementation
 */
contract TRC721 is Context, TRC165, ITRC721 {
    using Address for address;
    using Counters for Counters.Counter;

    // bytes4(keccak256("onTRC721Received(address,address,uint256,bytes)"))
    bytes4 private constant _TRC721_RECEIVED = 0x5175f878;

    mapping(uint256 => address) private _tokenOwner;
    mapping(uint256 => address) private _tokenApprovals;
    mapping(address => Counters.Counter) private _ownedTokensCount;
    mapping(address => mapping(address => bool)) private _operatorApprovals;

    bytes4 private constant _INTERFACE_ID_TRC721 = 0x80ac58cd;

    constructor() {
        _registerInterface(_INTERFACE_ID_TRC721);
    }

    function balanceOf(address owner) public view override returns (uint256) {
        require(owner != address(0), "TRC721: balance query for the zero address");
        return _ownedTokensCount[owner].current();
    }

    function ownerOf(uint256 tokenId) public view override returns (address) {
        address owner = _tokenOwner[tokenId];
        require(owner != address(0), "TRC721: owner query for nonexistent token");
        return owner;
    }

    function approve(address to, uint256 tokenId) public override {
        address owner = ownerOf(tokenId);
        require(to != owner, "TRC721: approval to current owner");
        require(
            _msgSender() == owner || isApprovedForAll(owner, _msgSender()),
            "TRC721: approve caller is not owner nor approved for all"
        );
        _tokenApprovals[tokenId] = to;
        emit Approval(owner, to, tokenId);
    }

    function getApproved(uint256 tokenId) public view override returns (address) {
        require(_exists(tokenId), "TRC721: approved query for nonexistent token");
        return _tokenApprovals[tokenId];
    }

    function setApprovalForAll(address to, bool approved) public override {
        require(to != _msgSender(), "TRC721: approve to caller");
        _operatorApprovals[_msgSender()][to] = approved;
        emit ApprovalForAll(_msgSender(), to, approved);
    }

    function isApprovedForAll(address owner, address operator) public view override returns (bool) {
        return _operatorApprovals[owner][operator];
    }

    function transferFrom(address from, address to, uint256 tokenId) public override {
        require(_isApprovedOrOwner(_msgSender(), tokenId), "TRC721: transfer caller is not owner nor approved");
        _transferFrom(from, to, tokenId);
    }

    function safeTransferFrom(address from, address to, uint256 tokenId) public override {
        safeTransferFrom(from, to, tokenId, "");
    }

    function safeTransferFrom(address from, address to, uint256 tokenId, bytes memory _data) public override {
        require(_isApprovedOrOwner(_msgSender(), tokenId), "TRC721: transfer caller is not owner nor approved");
        _safeTransferFrom(from, to, tokenId, _data);
    }

    function _safeTransferFrom(address from, address to, uint256 tokenId, bytes memory _data) internal {
        _transferFrom(from, to, tokenId);
        require(_checkOnTRC721Received(from, to, tokenId, _data), "TRC721: transfer to non TRC721Receiver implementer");
    }

    function _exists(uint256 tokenId) internal view returns (bool) {
        return _tokenOwner[tokenId] != address(0);
    }

    function _isApprovedOrOwner(address spender, uint256 tokenId) internal view returns (bool) {
        require(_exists(tokenId), "TRC721: operator query for nonexistent token");
        address owner = ownerOf(tokenId);
        return (spender == owner || getApproved(tokenId) == spender || isApprovedForAll(owner, spender));
    }

    function _safeMint(address to, uint256 tokenId) internal {
        _safeMint(to, tokenId, "");
    }

    function _safeMint(address to, uint256 tokenId, bytes memory _data) internal {
        _mint(to, tokenId);
        require(_checkOnTRC721Received(address(0), to, tokenId, _data), "TRC721: transfer to non TRC721Receiver implementer");
    }

    function _mint(address to, uint256 tokenId) internal virtual {
        require(to != address(0), "TRC721: mint to the zero address");
        require(!_exists(tokenId), "TRC721: token already minted");
        _tokenOwner[tokenId] = to;
        _ownedTokensCount[to].increment();
        emit Transfer(address(0), to, tokenId);
    }

    function _burn(address owner, uint256 tokenId) internal virtual {
        require(ownerOf(tokenId) == owner, "TRC721: burn of token that is not own");
        _clearApproval(tokenId);
        _ownedTokensCount[owner].decrement();
        _tokenOwner[tokenId] = address(0);
        emit Transfer(owner, address(0), tokenId);
    }

    function _burn(uint256 tokenId) internal {
        _burn(ownerOf(tokenId), tokenId);
    }

    function _transferFrom(address from, address to, uint256 tokenId) internal virtual {
        require(ownerOf(tokenId) == from, "TRC721: transfer of token that is not own");
        require(to != address(0), "TRC721: transfer to the zero address");
        _clearApproval(tokenId);
        _ownedTokensCount[from].decrement();
        _ownedTokensCount[to].increment();
        _tokenOwner[tokenId] = to;
        emit Transfer(from, to, tokenId);
    }

    /**
     * @dev Internal function to invoke {ITRC721Receiver-onTRC721Received} on a target address.
     * The call is not executed if the target address is not a contract.
     * [FIX H-08] isContract() is now a proper function call via Address library.
     */
    function _checkOnTRC721Received(address from, address to, uint256 tokenId, bytes memory _data)
        internal returns (bool)
    {
        if (!to.isContract()) {
            return true;
        }
        (bool success, bytes memory returndata) = to.call(
            abi.encodeWithSelector(
                ITRC721Receiver(to).onTRC721Received.selector,
                _msgSender(),
                from,
                tokenId,
                _data
            )
        );
        if (!success) {
            if (returndata.length > 0) {
                assembly {
                    let returndata_size := mload(returndata)
                    revert(add(32, returndata), returndata_size)
                }
            } else {
                revert("TRC721: transfer to non TRC721Receiver implementer");
            }
        } else {
            bytes4 retval = abi.decode(returndata, (bytes4));
            return (retval == _TRC721_RECEIVED);
        }
    }

    function _clearApproval(uint256 tokenId) private {
        if (_tokenApprovals[tokenId] != address(0)) {
            _tokenApprovals[tokenId] = address(0);
        }
    }
}

/**
 * @title TRC721 with metadata extension
 */
abstract contract TRC721Metadata is Context, TRC165, TRC721, ITRC721Metadata {
    string private _name;
    string private _symbol;
    string private _baseURI;
    mapping(uint256 => string) private _tokenURIs;

    bytes4 private constant _INTERFACE_ID_TRC721_METADATA = 0x5b5e139f;

    constructor(string memory name_, string memory symbol_) {
        _name = name_;
        _symbol = symbol_;
        _registerInterface(_INTERFACE_ID_TRC721_METADATA);
    }

    function name() external view override returns (string memory) {
        return _name;
    }

    function symbol() external view override returns (string memory) {
        return _symbol;
    }

    function tokenURI(uint256 tokenId) external view override returns (string memory) {
        require(_exists(tokenId), "TRC721Metadata: URI query for nonexistent token");
        string memory _tokenURI = _tokenURIs[tokenId];
        if (bytes(_tokenURI).length == 0) {
            return "";
        }
        return string(abi.encodePacked(_baseURI, _tokenURI));
    }

    function _setTokenURI(uint256 tokenId, string memory _tokenURI) internal {
        require(_exists(tokenId), "TRC721Metadata: URI set of nonexistent token");
        _tokenURIs[tokenId] = _tokenURI;
    }

    function _setBaseURI(string memory baseURI_) internal {
        _baseURI = baseURI_;
    }

    function baseURI() external view returns (string memory) {
        return _baseURI;
    }

    function _burn(address owner, uint256 tokenId) internal virtual override {
        super._burn(owner, tokenId);
        if (bytes(_tokenURIs[tokenId]).length != 0) {
            delete _tokenURIs[tokenId];
        }
    }
}

/**
 * @title TRC721MetadataMintable
 */
contract TRC721MetadataMintable is TRC721, TRC721Metadata, MinterRole {
    function mintWithTokenURI(address to, uint256 tokenId, string memory tokenURI_)
        public onlyMinter returns (bool)
    {
        _mint(to, tokenId);
        _setTokenURI(tokenId, tokenURI_);
        return true;
    }
}

/**
 * @title TRC721Mintable
 */
contract TRC721Mintable is TRC721, MinterRole {
    function mint(address to, uint256 tokenId) public onlyMinter returns (bool) {
        _mint(to, tokenId);
        return true;
    }

    function safeMint(address to, uint256 tokenId) public onlyMinter returns (bool) {
        _safeMint(to, tokenId);
        return true;
    }

    function safeMint(address to, uint256 tokenId, bytes memory _data) public onlyMinter returns (bool) {
        _safeMint(to, tokenId, _data);
        return true;
    }
}

/**
 * @title TRC721 with enumeration extension
 */
contract TRC721Enumerable is Context, TRC165, TRC721, ITRC721Enumerable {
    mapping(address => uint256[]) private _ownedTokens;
    mapping(uint256 => uint256) private _ownedTokensIndex;
    uint256[] private _allTokens;
    mapping(uint256 => uint256) private _allTokensIndex;

    bytes4 private constant _INTERFACE_ID_TRC721_ENUMERABLE = 0x780e9d63;

    constructor() {
        _registerInterface(_INTERFACE_ID_TRC721_ENUMERABLE);
    }

    function tokenOfOwnerByIndex(address owner, uint256 index) public view override returns (uint256) {
        require(index < balanceOf(owner), "TRC721Enumerable: owner index out of bounds");
        return _ownedTokens[owner][index];
    }

    function totalSupply() public view override returns (uint256) {
        return _allTokens.length;
    }

    function tokenByIndex(uint256 index) public view override returns (uint256) {
        require(index < totalSupply(), "TRC721Enumerable: global index out of bounds");
        return _allTokens[index];
    }

    function _transferFrom(address from, address to, uint256 tokenId) internal override {
        super._transferFrom(from, to, tokenId);
        _removeTokenFromOwnerEnumeration(from, tokenId);
        _addTokenToOwnerEnumeration(to, tokenId);
    }

    function _mint(address to, uint256 tokenId) internal virtual override {
        super._mint(to, tokenId);
        _addTokenToOwnerEnumeration(to, tokenId);
        _addTokenToAllTokensEnumeration(tokenId);
    }

    function _burn(address owner, uint256 tokenId) internal virtual override {
        super._burn(owner, tokenId);
        _removeTokenFromOwnerEnumeration(owner, tokenId);
        _ownedTokensIndex[tokenId] = 0;
        _removeTokenFromAllTokensEnumeration(tokenId);
    }

    function _tokensOfOwner(address owner) internal view returns (uint256[] storage) {
        return _ownedTokens[owner];
    }

    function _addTokenToOwnerEnumeration(address to, uint256 tokenId) private {
        _ownedTokensIndex[tokenId] = _ownedTokens[to].length;
        _ownedTokens[to].push(tokenId);
    }

    function _addTokenToAllTokensEnumeration(uint256 tokenId) private {
        _allTokensIndex[tokenId] = _allTokens.length;
        _allTokens.push(tokenId);
    }

    function _removeTokenFromOwnerEnumeration(address from, uint256 tokenId) private {
        uint256 lastTokenIndex = _ownedTokens[from].length - 1;
        uint256 tokenIndex = _ownedTokensIndex[tokenId];
        if (tokenIndex != lastTokenIndex) {
            uint256 lastTokenId = _ownedTokens[from][lastTokenIndex];
            _ownedTokens[from][tokenIndex] = lastTokenId;
            _ownedTokensIndex[lastTokenId] = tokenIndex;
        }
        _ownedTokens[from].pop();
    }

    function _removeTokenFromAllTokensEnumeration(uint256 tokenId) private {
        uint256 lastTokenIndex = _allTokens.length - 1;
        uint256 tokenIndex = _allTokensIndex[tokenId];
        uint256 lastTokenId = _allTokens[lastTokenIndex];
        _allTokens[tokenIndex] = lastTokenId;
        _allTokensIndex[lastTokenId] = tokenIndex;
        _allTokens.pop();
        _allTokensIndex[tokenId] = 0;
    }
}

/**
 * @title TRC721Token
 * @dev Full TRC-721 token implementation with enumeration and mintable metadata.
 *      Replace "Your Token Name" and "YTN" with your token's name and symbol.
 */
contract TRC721Token is TRC721Enumerable, TRC721MetadataMintable {
    constructor() TRC721Metadata("Your Token Name", "YTN") {}
}