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ERC721解读_erc721合约设计

作者：凡人多烦事01 | 2024-06-13 18:49:16

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erc721合约设计

NFT(非同质化代币):类似于明朝、宋朝的青花瓷。虽然都是青花瓷。但是都具有唯一的典藏价值。而且价值可能不同。 NFT就是具有唯一价值的代币。

ERC721: 是以太坊规定实现NFT的一种标准了。实现ERC21标准的智能合约就是NFT代币了。

1.接口

1.ERC721

  定义接口参考：ERC 721 - OpenZeppelin 文档

下面是以太坊官方定义的标准,由于就是我写的代码运行环境不支持payable关键字，因此我打算围绕官方接口定义，按照自己要求稍微增删一下。

  1. pragma solidity ^0.4.25;
  2.  
  3. interface ERC721 {
  4.     
  5.     ///
  6.      Event
  7.     ///
  8.     event Transfer(address indexed _from, address indexed _to, uint256 indexed _tokenId);
  9.     event Approval(address indexed _owner, address indexed _approved, uint256 indexed _tokenId);
  10.     event ApprovalForAll(address indexed _owner, address indexed _operator, bool _approved);
  11.  
  12.  
  13.     ///
  14.      Function
  15.     ///
  16.     function balanceOf(address _owner) external view returns (uint256); // 返回所有者代币的总个数
  17.     function ownerOf(uint256 _tokenId) external view returns (address); // 返回代币id对应所有者的账户地址
  18.     // 安全的转账
  19.     //  _to:是已经被指定 id 代币的所有者授予的账户 and (接受者不是智能合约 or 接受者实现ERC721Receiver接口的智能合约
  20.     // 将给定id的代币转移到接受者账户
  21.     // data是元数据，可有可不有(我觉得)
  22.     function safeTransferFrom(address _from, address _to, uint256 _tokenId, bytes data) external; 
  23.     function safeTransferFrom(address _from, address _to, uint256 _tokenId) external;
  24.     // 这个转账对比上述安全转账(少了一个接受者地址实现是否是ERC721Receiver接口的智能合约地址的判断)
  25.     function transferFrom(address _from, address _to, uint256 _tokenId) external;
  26.     // 授权将代币转移到另一个账户的权限
  27.     function approve(address _approved, uint256 _tokenId) external;
  28.     // 授权接受者使用所有代币
  29.     function setApprovalForAll(address _operator, bool _approved) external;
  30.     // 返回授权指定id 代币的接受者账户
  31.     function getApproved(uint256 _tokenId) external view returns (address);
  32.     // 判断某账户代币的拥有者是否能被某账户全部使用
  33.     function isApprovedForAll(address _owner, address _operator) external view returns (bool);
  34. }
  35.

2.ERC721Metadata

以下就是ERC21的元数据接口，这是可选地。名称、标识符、每一个token对应的tokenURI。

  1. pragma solidity ^0.4.25;
  2.  
  3. interface ERC721Metadata {
  4.     function name() external view returns (string);
  5.     function symbol() external view returns (string);
  6.     function tokenURI(uint256 tokenId) external view returns (string); // 返回指定id的代币所对对应的uri
  7. }

3.ERC721Enumerable

另一个额外的可选接口是枚举， 它包含了按索引获取到对应的代币。

  1. pragma solidity ^0.4.25;
  2.  
  3. interface ERC721Enumerable {
  4.     // 确定合约当前全部的nft数量(出去销毁)
  5.     function totalSupply() external view returns (uint256);
  6.     // 从代币列表返回第n个代币
  7.     function tokenByIndex(uint256 _index) external view returns (uint256);
  8.     // 返回所有者代币列表的第n个代币
  9.     function tokenOfOwnerByIndex(address _owner, uint256 _index) external view returns (uint256);
  10. }

4.ERC721Receiver

  1. pragma solidity ^0.4.25;
  2.  
  3. // 资产合约
  4. interface ERC721Receiver {
  5.     function onERC721Received(address operator, address from, uint256 tokenId, bytes data) external
  6.         returns (bytes);
  7. }

2.实现

1.Jzm721

这是我针对ERC721接口的合约实现。基本满足官方接口标准。

  1. pragma solidity ^0.4.25;
  2. import "./ERC721.sol";
  3. import "./ERC721Metadata.sol";
  4. contract Jzm721 is ERC721,ERC721Metadata {
  5.  
  6.     ///
  7.      Filed
  8.     ///
  9.     string public name;
  10.     string public symbol;
  11.     uint256  nftCount;
  12.     mapping (address => uint[])  balanceMap; // owner => tokenId[]
  13.     mapping (uint256=>string)  tokenURIMap; // tokenId => tokenURI
  14.     mapping (uint256=>address)  tokenIdMap; // tokenId => owner
  15.     mapping (uint256 => address) approveMap; // tokenId => operator(经营方)
  16.     mapping (address=>mapping (address=>bool)) approveAllMap; // operator =>(owner => true/false)
  17.  
  18.     ///
  19.      Function
  20.     ///
  21.     constructor(string memory _name,string memory _symbol) 
  22.     public {
  23.         name = _name;
  24.         symbol = _symbol;
  25.     }
  26.  
  27.     function name() external view returns (string) {
  28.         return name;
  29.     }
  30.  
  31.     function symbol() external view returns (string) {
  32.         return symbol;
  33.     }
  34.  
  35.     function tokenURI(uint256 tokenId) external view returns (string) {
  36.         return tokenURIMap[tokenId];
  37.     }
  38.  
  39.     // 创建代币
  40.     function mint(address _owner,string _tokenURI) external  returns (uint256) {
  41.         require(_owner != address(0),"owner is not empty address!");
  42.         uint256 tokenId = _mint(_owner);
  43.         _setTokenURI(tokenId, _tokenURI);
  44.         return tokenId;
  45.     }
  46.  
  47.     function balanceOf(address _owner) external view returns (uint256) {
  48.         return balanceMap[_owner].length;
  49.     }
  50.  
  51.     function ownerOf(uint256 _tokenId) external view returns (address) {
  52.         return tokenIdMap[_tokenId];
  53.     }
  54.  
  55.     // 这里我忽略了data这个元数据的作用
  56.     function safeTransferFrom(address _from, address _to, uint256 _tokenId, bytes data) external {
  57.         _transferFrom(_from, _to, _tokenId);
  58.         if(_isContractAdd(_to)) {
  59.             if(_checkIfFunctionExists(_to)) {
  60.                 _externalTransfer(_from, _to, _tokenId);
  61.                 emit Transfer(_from, _to, _tokenId);
  62.             }  
  63.         }
  64.     }
  65.  
  66.     function safeTransferFrom(address _from, address _to, uint256 _tokenId) external {
  67.         _transferFrom(_from, _to, _tokenId);
  68.         if(_isContractAdd(_to)) {
  69.             if(_checkIfFunctionExists(_to)) {
  70.                 _externalTransfer(_from, _to, _tokenId);
  71.                 emit Transfer(_from, _to, _tokenId);
  72.             }
  73.         }
  74.     }
  75.  
  76.     function transferFrom(address _from, address _to, uint256 _tokenId) external {
  77.         _transferFrom(_from, _to, _tokenId);
  78.     }
  79.  
  80.  
  81.     function approve(address _approved, uint256 _tokenId) external {
  82.         require(_approved != address(0),"approved is not empty address!");
  83.         address owner = msg.sender;
  84.         approveMap[_tokenId] = _approved; 
  85.         emit Approval(owner,_approved,_tokenId);
  86.     }
  87.  
  88.     function setApprovalForAll(address _operator, bool _approved) external {
  89.         require(_operator != address(0),"operator is not empty address!");
  90.         address owner = msg.sender;
  91.         approveAllMap[_operator][owner] = _approved;
  92.         emit  ApprovalForAll(owner,_operator,_approved);
  93.     }
  94.  
  95.     function getApproved(uint256 _tokenId) external view returns (address) {
  96.         return _getApproved(_tokenId);
  97.     }
  98.  
  99.     function isApprovedForAll(address _owner, address _operator) external view returns (bool) {
  100.         return _isApprovedForAll(_owner,_operator);
  101.     }
  102.  
  103.     function _checkIfFunctionExists(address _add)public  returns (bool) {
  104.         bytes4 functionSelector = bytes4(keccak256("onERC721Received(address,address,uint256,bytes)")); // 函数选择器，基础原型前4个字节
  105.         bytes memory data = abi.encodeWithSelector(functionSelector, address(0),address(0),0,"");
  106.         bool success = _add.call(data);
  107.         return success;
  108.     }
  109.  
  110.     function _transferFrom(address _from, address _to, uint256 _tokenId) private {
  111.         // from不能是零地址。
  112.         require(_from != address(0),"from is not empty address!");
  113.         // to不能是零地址。
  114.         require(_to != address(0),"from is not empty address!");
  115.         // tokenId令牌必须存在并由from拥有。
  116.         require(tokenIdMap[_tokenId] == _from,"The tokenId  must exist and be owned by from!");
  117.         // 接受者一方不是合约地址
  118.         if (!_isContractAdd(_to)) {
  119.             if (_isApproved(_from, _to, _tokenId)) { 
  120.                 // TODO
  121.                 _externalTransfer(_from, _to, _tokenId);
  122.                 emit Transfer(_from, _to, _tokenId);
  123.             }
  124.         }
  125.     }
  126.  
  127.     function _externalTransfer(address _from,address _to,uint256 _tokenId) private {
  128.         // 删除代币批准
  129.         if(_getApproved(_tokenId) == _to) {
  130.             approveMap[_tokenId] = address(0);   
  131.         }
  132.         // 转账
  133.         _deleteAccountToken(_from,_tokenId);
  134.         tokenIdMap[_tokenId] = _to;
  135.         balanceMap[_to].push(_tokenId);
  136.     }
  137.  
  138.  
  139.     function _deleteAccountToken(address _owner,uint256 _tokenId) private {
  140.         uint256[] storage tokenIds = balanceMap[_owner];
  141.         uint len =  tokenIds.length;
  142.         for (uint i = 0; i < len; i++) {
  143.             if(tokenIds[i] == _tokenId) {
  144.                 // 交换
  145.                 uint swap;
  146.                 swap = tokenIds[i];
  147.                 tokenIds[i] = tokenIds[len - 1];
  148.                 tokenIds[len - 1] = swap;
  149.             }
  150.         }
  151.         tokenIds.length--;
  152.     }
  153.  
  154.     function _mint(address _owner) private  returns (uint256) {
  155.         nftCount += 1;
  156.         uint256 tokenId = nftCount + block.timestamp;
  157.         balanceMap[_owner].push(tokenId);
  158.         tokenIdMap[tokenId] = _owner;
  159.         emit Transfer(address(0),_owner,tokenId);
  160.         return tokenId;
  161.     }
  162.  
  163.     function _setTokenURI(uint256 _tokenId,string _tokenURI) private{
  164.         tokenURIMap[_tokenId] = _tokenURI;
  165.     }
  166.  
  167.     // 判断该地址是否合约地址
  168.     function _isContractAdd(address  _addr) private view returns (bool) {
  169.         uint size;
  170.         assembly {
  171.             size := extcodesize(_addr) // 返回地址关联代码的长度
  172.         }
  173.         return size > 0;
  174.     }
  175.  
  176.     function _getApproved(uint256 _tokenId) private view returns(address) {
  177.         return approveMap[_tokenId];
  178.     }
  179.  
  180.     function _isApproved(address _owner, address _operator,uint256 _tokenId) private view returns (bool) {
  181.         bool approved = _getApproved(_tokenId) == _operator;
  182.         return approved || _isApprovedForAll(_owner, _operator);
  183.     }
  184.  
  185.     function _isApprovedForAll(address _owner, address _operator) private view returns(bool) {
  186.         return approveAllMap[_operator][_owner];
  187.     }
  188.  
  189.  
  190.  
  191.  
  192. }
  193.

2.Jzm721Receiver

在这里我就是想要满足合约地址的合约实现ERC721Receiver接口的标准。原合约，这里该函数涉及代币的转账，由于环境的原因，不支持payable关键字，我这里是无法满足的。

  1. pragma solidity ^0.4.25;
  2. import "./ERC721Receiver.sol";
  3.  
  4. contract Jzm721Receiver is ERC721Receiver {
  5.     function onERC721Received(address operator, address from, uint256 tokenId, bytes data) external
  6.         returns (bytes) {
  7.             return data;
  8.         }
  9. }

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