从0开发一个Dapp

实现效果

1. 房主发送拍卖房屋信息，并且设置拍卖过期时间

2. 其它非房主可以登录进行拍卖，选择自己的出价

参考

https://dev.to/yongchanghe/build-a-simple-dapp-using-truffle-ganache-ethersjs-and-react1-52bl

工具集合

1. 安装node，版本是v16.16.0
2. npm install -g truffle, truffle可以让我们在本地开发合约，同时部署合约到链上。
3. 安装ganache， ganache相当于是把以太网部署在本地，我们可以把合约发布到本地的以太网上。
4. metamask，钱包可以添加账户，查看我们的账户余额，

初始化项目

1. mkdir web3-ticket && truffle init

2. 项目目录如下

3. 修改truffle.config.js的development

4. 打开Ganache，新建workspace，选择项目的trffle.config.js

然后我们就可以看到很多账号了，而且里边还有余额

这样我们就可以通过truffle，连接到链上，同时部署合约到这里了

5. 在web3-ticket/contracts下新建拍卖合约，Auction.sol，代码比较简单，关键地方都已经添加注释。

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.17;

contract Auction {
 // Properties
 // 定义owner地址
 address private owner;
 uint256 public startTime;
 uint256 public endTime;
 // 映射
 mapping(address => uint256) public bids;

// 结构体
 struct House {
   string houseType;
   string houseColor;
   string houseLocation;
 }

// 最高出价，竞拍，最高价
 struct HighestBid {
   uint256 bidAmount;
   address bidder;
 }

 House public newHouse;
 HighestBid public highestBid;

 // Insert modifiers here
 // Modifiers
 // 竞拍已经结束
 modifier isOngoing() {
   require(block.timestamp < endTime, 'This auction is closed.');
   _;
 }
 // 竞拍还在进行
 modifier notOngoing() {
   require(block.timestamp >= endTime, 'This auction is still open.');
   _;
 }
 // 是不是作者，如果不是没有权限
 modifier isOwner() {
   require(msg.sender == owner, 'Only owner can perform task.');
   _;
 }
 // 不是作者
 modifier notOwner() {
   require(msg.sender != owner, 'Owner is not allowed to bid.');
   _;
 }
 // Insert events here
 // Events，允许前端调用事件
 event LogBid(address indexed _highestBidder, uint256 _highestBid);
 event LogWithdrawal(address indexed _withdrawer, uint256 amount);
 // Insert constructor and function here
 // Assign values to some properties during deployment
 constructor () {
   owner = msg.sender;
   startTime = block.timestamp;
   endTime = block.timestamp + 12 hours;
   newHouse.houseColor = '#FFFFFF';
   newHouse.houseLocation = 'Sask, SK';
   newHouse.houseType = 'Townhouse';
 }

// makeBid 开始竞价，房子必须是在拍卖中，并且不能房主自己出价
 function makeBid() public payable isOngoing() notOwner() returns (bool) {
   uint256 bidAmount = bids[msg.sender] + msg.value;
   // 当前出价要高于前面的出价，不然报错
   require(bidAmount > highestBid.bidAmount, 'Bid error: Make a higher Bid.');

   highestBid.bidder = msg.sender;
   highestBid.bidAmount = bidAmount;
   bids[msg.sender] = bidAmount;
   emit LogBid(msg.sender, bidAmount);
   return true;
 }

// 付款
 function withdraw() public notOngoing() isOwner() returns (bool) {
   uint256 amount = highestBid.bidAmount;
   bids[highestBid.bidder] = 0;
   highestBid.bidder = address(0);
   highestBid.bidAmount = 0;
  // 向房主付款
   (bool success, ) = payable(owner).call{ value: amount }("");
   require(success, 'Withdrawal failed.');
   emit LogWithdrawal(msg.sender, amount);
   return true;
 }
 // 获取最高出价
 function fetchHighestBid() public view returns (HighestBid memory) {
   HighestBid memory _highestBid = highestBid;
   return _highestBid;
 }
 // 获得当前房主
 function getOwner() public view returns (address) {
   return owner;
 }
}

6. 执行compile

truffle compile

7. 添加部署文件，在migrations下面添加2_initial_migrations.js

const Auction = artifacts.require("Auction");

module.exports = function (deployer) {
  deployer.deploy(Auction);
};

8. 在test下新建测试文件Auctioin.test.js

const Auction = artifacts.require("Auction");

contract("Auction", async (accounts) => {
  let auction;
  const ownerAccount = accounts[0];
  const userAccountOne = accounts[1];
  const userAccountTwo = accounts[2];
  const amount = 5000000000000000000; // 5 ETH
  const smallAmount = 3000000000000000000; // 3 ETH

  beforeEach(async () => {
    auction = await Auction.new({ from: ownerAccount });
  });

  it("should make bid.", async () => {
    await auction.makeBid({ value: amount, from: userAccountOne });
    const bidAmount = await auction.bids(userAccountOne);
    assert.equal(bidAmount, amount);
  });

  it("should reject owner's bid.", async () => {
    try {
      await auction.makeBid({ value: amount, from: ownerAccount });
    } catch (e) {
      assert.include(e.message, "Owner is not allowed to bid.");
    }
  });

  it("should require higher bid amount.", async () => {
    try {
      await auction.makeBid({ value: amount, from: userAccountOne });
      await auction.makeBid({ value: smallAmount, from: userAccountTwo });
    } catch (e) {
      assert.include(e.message, "Bid error: Make a higher Bid.");
    }
  });

  it("should fetch highest bid.", async () => {
    await auction.makeBid({ value: amount, from: userAccountOne });
    const highestBid = await auction.fetchHighestBid();
    assert.equal(highestBid.bidAmount, amount);
    assert.equal(highestBid.bidder, userAccountOne);
  });

  it("should fetch owner.", async () => {
    const owner = await auction.getOwner();
    assert.equal(owner, ownerAccount);
  });
});

然后执行

truffle develop
test

如果出现下图，说明测试成功

完成后目录文件如下

9. 使用creact-react-app，在web3-ticket目录下

安装依赖

cd client
npm install ethers @ethersproject/units

10. 修改truuffle.config.js的配置,配置合约的输出目录

11. 发布合约到本地的链上，也就是Ganache模式的链上，因为前面已经启动过了，这里直接发布就可以。

出现下图，说明已经成功部署。

可以看到，部署成功，因为每次需要消耗ETH,所以这里从100ETH到99.98 ETH

同时可以发现在前端的目录client下，增加了contracts目录，如下图

12. 修改client/src/app.js

import "./App.css";
import { useEffect, useState } from "react";
import { ethers } from "ethers";
import { parseEther, formatEther } from "@ethersproject/units";
import Auction from "./contracts/Auction.json";
// 这里的地址是前面合约部署成功之后的合约地址
const AuctionContractAddress = "0xD50acf2Aaa9183b2aC00cd4D27bC3145c919013d";
const emptyAddress = "0x0000000000000000000000000000000000000000";

function App() {
  // Use hooks to manage component state
  const [account, setAccount] = useState("");
  const [amount, setAmount] = useState(0);
  const [myBid, setMyBid] = useState(0);
  const [isOwner, setIsOwner] = useState(false);
  const [highestBid, setHighestBid] = useState(0);
  const [highestBidder, setHighestBidder] = useState("");

  // Sets up a new Ethereum provider and returns an interface for interacting with the smart contract
  // 使用ethers获取合约
  async function initializeProvider() {
    const provider = new ethers.providers.Web3Provider(window.ethereum);
    const signer = provider.getSigner();
    return new ethers.Contract(AuctionContractAddress, Auction.abi, signer);
  }

  // Displays a prompt for the user to select which accounts to connect
  // 弹出钱包，让我们选择账户
  async function requestAccount() {
    const account = await window.ethereum.request({
      method: "eth_requestAccounts",
    });
    setAccount(account[0]);
  }
  // 获取最高出价
  async function fetchHighestBid() {
    if (typeof window.ethereum !== "undefined") {
      const contract = await initializeProvider();
      try {
        const highestBid = await contract.fetchHighestBid();
        const { bidAmount, bidder } = highestBid;

        // Convert bidAmount from Wei to Ether and round value to 4 decimal places
        setHighestBid(
          parseFloat(formatEther(bidAmount.toString())).toPrecision(4)
        );
        setHighestBidder(bidder.toLowerCase());
      } catch (e) {
        console.log("error fetching highest bid: ", e);
      }
    }
  }

  async function fetchMyBid() {
    if (typeof window.ethereum !== "undefined") {
      const contract = await initializeProvider();
      try {
        const myBid = await contract.bids(account);
        setMyBid(parseFloat(formatEther(myBid.toString())).toPrecision(4));
      } catch (e) {
        console.log("error fetching my bid: ", e);
      }
    }
  }

  async function fetchOwner() {
    if (typeof window.ethereum !== "undefined") {
      const contract = await initializeProvider();
      try {
        const owner = await contract.getOwner();
        setIsOwner(owner.toLowerCase() === account);
      } catch (e) {
        console.log("error fetching owner: ", e);
      }
    }
  }
  // 提价出价
  async function submitBid(event) {
    event.preventDefault();
    if (typeof window.ethereum !== "undefined") {
      const contract = await initializeProvider();
      try {
        // User inputs amount in terms of Ether, convert to Wei before sending to the contract.
        const wei = parseEther(amount);
        await contract.makeBid({ value: wei });
        // Wait for the smart contract to emit the LogBid event then update component state
        contract.on("LogBid", (_, __) => {
          fetchMyBid();
          fetchHighestBid();
        });
      } catch (e) {
        console.log("error making bid: ", e);
      }
    }
  }
  // 房屋主人获取转账
  async function withdraw() {
    if (typeof window.ethereum !== "undefined") {
      const contract = await initializeProvider();
      // Wait for the smart contract to emit the LogWithdrawal event and update component state
      contract.on("LogWithdrawal", (_) => {
        fetchMyBid();
        fetchHighestBid();
      });
      try {
        await contract.withdraw();
      } catch (e) {
        console.log("error withdrawing fund: ", e);
      }
    }
  }

  useEffect(() => {
    requestAccount();
  }, []);

  useEffect(() => {
    if (account) {
      fetchOwner();
      fetchMyBid();
      fetchHighestBid();
    }
  }, [account]);

  return (
    

      {isOwner ? (
        
          Withdraw
        
      ) : (
        ""
      )}
      

        
连接的账户是: {account}
        
我的出价: {myBid}
        
拍卖出价最高是: {highestBid}
        

          拍卖出价最高账户是:{" "}
          {highestBidder === emptyAddress
            ? "null"
            : highestBidder === account
            ? "Me"
            : highestBidder}
        
        {!isOwner ? (
          

             setAmount(event.target.value)}
              name="Bid Amount"
              type="number"
              placeholder="Enter Bid Amount"
            />
            提交
          
        ) : (
          ""
        )}
      
    
  );
}

export default App;

13. chrome安装metamask

安装过程比较简单，最主要的是要把钱包的助记词记好

这里主要是需要把钱包连接到Ganache启动的链上，点击增加Add Network

把这里的地址复制进去

效果如下图

然后选择连接上Ganache

在Ganache中查看账号，通过私钥导入账号，这里我们导入两个账号

效果如下

14. 启动前端

npm start

启动服务，会弹出metamask，首先选择Account3，因为Account2是房主自己，Account1是默认添加的。

这里因为是需要输入拍卖假，我们选择10个ETH,查看效果

可以看到这里就弹出metamask，让我们确认我们是否转入10ETH,

我们点击confirm，可以看到我们账号已经少了10ETH

我们再在metamask里边切换会房屋主人的查看页面，选择Account2，看看效果

我们就可以看到最高出价的账户是哪一个。

当我们点击withDraw的时候，发现如下错误

关键的错误是指这里

我们去合约代码Auction.sol里边查看,发现是函数装饰器抛出的错误,因为我们在endTime里边设置的拍卖时间是12个小时，所以这里还在拍卖中，所以房主不能结束拍卖。

 // Assign values to some properties during deployment
 constructor () {
   owner = msg.sender;
   startTime = block.timestamp;
   endTime = block.timestamp + 12 hours;
   newHouse.houseColor = '#FFFFFF';
   newHouse.houseLocation = 'Sask, SK';
   newHouse.houseType = 'Townhouse';
 }

 // 竞拍还在进行
 modifier notOngoing() {
   require(block.timestamp >= endTime, 'This auction is still open.');
   _;
 }

这里我们可以等待12小时之后，房主再上来点击witdhDraw或者重新编译部署合约，
这里我们选择重新编译部署合约
这里我们把Auction.sol里边的结束时间，设置为5 minutes

 constructor () {
   owner = msg.sender;
   startTime = block.timestamp;
   endTime = block.timestamp + 5 minutes;
   newHouse.houseColor = '#FFFFFF';
   newHouse.houseLocation = 'Sask, SK';
   newHouse.houseType = 'Townhouse';
 }

重新测试

重新comile

重新部署

这里我们看到部署的地址发生了改变

我们需要把contract address，复制到前端代码的这里替换
在client/src/app.js

// 这里是前面部署合约的时候的contract address
// 最新部署地址
const AuctionContractAddress = "0xAf0C3Db2cC621254E5394B538abdbC50bB860b04";
// 以前部署的地址
// const AuctionContractAddress = "0xe83CfD83BFcb732f207C1Ba94eD4341170667A07";

然后还是先选择Account3 出价竞拍，然后再切换回Account2，查看

等等超过5分钟再看

然后我们去我们账户中查看，可以看到

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