【学习】自建一个简单的NFT721交易所

最近又学习了ERC721相关的接口和合约，写一个能够简单交易NFT的交易所进行锻炼。

• 主要知识点包括：

1、ERC721合约和接口

2、ERCReceiver的接口主要用途

3、使用Openzeppelin合约库

4、Remix在线编码平台使用

目前总觉得给合约，函数，变量起名字很累，当然也包括注释和说明内容，英文表述还是困难。

• 合约代码：

看下写的NFT交易所的代码吧。

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.10; 

import "@openzeppelin/contracts/token/ERC721/ERC721.sol";
import "@openzeppelin/contracts/token/ERC721/IERC721.sol";
import "@openzeppelin/contracts/token/ERC721/IERC721Receiver.sol";


 contract  NFTSwap is ERC721,IERC721Receiver {

    struct NftOrder {
        address owner;
        uint256 price;
    }

    mapping(address => mapping(uint256 => NftOrder)) public nftMarket ;

    event SellNft(address indexed nft, address indexed owner, uint256 id, uint256 price );
    event RevokeNft(address indexed nft, address indexed owner, uint256 id);
    event UpdateNft(address indexed nft, address indexed owner, uint256 id, uint256 newprice);
    event BuyNft(address indexed nft, address buyer, address indexed owner, uint256 price);

    constructor () ERC721("NFTSWAP", "NFTSWAP"){}

    receive() payable external {
    }

    function sellNft (address nft, uint256 id, uint256 price) public {
        require (nft != address(0), "nft address is 0");
        require (price > 0 , "price can not 0");
        require (IERC721(nft).getApproved(id) == address(this), "not approved");
        NftOrder storage no = nftMarket[nft][id];
        no.owner = msg.sender;
        no.price = price;

        IERC721(nft).safeTransferFrom(msg.sender, address(this), id);
        emit SellNft(nft, msg.sender, id, price);
    }

    function revokeNft(address nft, uint256 id) public {
        require (nft != address(0), "nft address is 0");
        NftOrder memory no = nftMarket[nft][id];
        require (no.owner == msg.sender, "not nft owner");
        IERC721(nft).safeTransferFrom(address(this), no.owner, id);
        delete nftMarket[nft][id];
        emit RevokeNft(nft, msg.sender, id);
    }

    function updateNft(address nft, uint256 id, uint256 newprice) public {
        require (nft != address(0), "nft address is 0");
        NftOrder storage no = nftMarket[nft][id];
        require (no.owner == msg.sender, "not nft owner");
        no.price = newprice;
        emit UpdateNft(nft, msg.sender, id, newprice);
    }

    function buyNft(address nft, uint256 id) public payable {
        require (nft != address(0), "nft address is 0");
        NftOrder storage no = nftMarket[nft][id];
        require (msg.value >= no.price, "not enough eth");
        require (no.owner != msg.sender, "nft owner cannot buy");
        payable(no.owner).transfer(no.price);
        IERC721(nft).safeTransferFrom(address(this), msg.sender, id);
        emit BuyNft(nft, msg.sender, no.owner, no.price);
        delete nftMarket[nft][id];
    }
          // 实现{IERC721Receiver}的onERC721Received，能够接收ERC721代币
      function onERC721Received(
          address operator,
          address from,
          uint tokenId,
          bytes calldata data
      ) external pure override returns (bytes4){
          return IERC721Receiver.onERC721Received.selector;
      }
}

• 主要事件：

 event SellNft(address indexed nft, address indexed owner, uint256 id, uint256 price );
 event RevokeNft(address indexed nft, address indexed owner, uint256 id);
 event UpdateNft(address indexed nft, address indexed owner, uint256 id, uint256 newprice);
 event BuyNft(address indexed nft, address buyer, address indexed owner, uint256 price);

• 主要函数：

function sellNft (address nft, uint256 id, uint256 price) public;

function revokeNft(address nft, uint256 id) public;

function updateNft(address nft, uint256 id, uint256 newprice) public;

function buyNft(address nft, uint256 id) public payable;

function onERC721Received(

address operator,

address from,

uint tokenId,

bytes calldata data

) external pure override returns (bytes4);

• Remix实践截图（需要提前部署一个NFT721合约）