Category: Blockchain

pragma solidity ^0.8.0;

interface IERC20 {
    function transfer(address to, uint256 amount) external returns (bool);
    function transferFrom(address from, address to, uint256 amount) external returns (bool);
}

contract SimpleSwap {
    address public owner;
    IERC20 public token;
    uint256 public rate;

    constructor(address _tokenAddress, uint256 _rate) {
        owner = msg.sender;
        token = IERC20(_tokenAddress);
        rate = _rate;
    }

    receive() external payable {
        uint256 tokenAmount = msg.value * rate;
        require(token.transfer(msg.sender, tokenAmount), "Token transfer failed");
    }

    function swapTokenForETH(uint256 tokenAmount) external {
        uint256 ethAmount = tokenAmount / rate;
        require(address(this).balance >= ethAmount, "Not enough ETH in contract");

        require(token.transferFrom(msg.sender, address(this), tokenAmount), "Token transfer failed");

        (bool success, ) = msg.sender.call{value: ethAmount}("");
        require(success, "ETH transfer failed");
    }

    function withdrawETH() external {
        require(msg.sender == owner, "Not owner");
        payable(owner).transfer(address(this).balance);
    }

    function withdrawTokens() external {
        require(msg.sender == owner, "Not owner");
        uint256 balance = tokenBalance();
        require(token.transfer(owner, balance), "Token withdrawal failed");
    }

    function tokenBalance() public view returns (uint256) {
        return token.balanceOf(address(this));
    }
}

sendではなく、recipient.callで送信してますね。

pragma solidity ^0.8.0;

constract ConditionTransfer {
    address public owner;
    address payable public recipient;
    uint256 public unlockTime;

    constructor(address payable _recipient, uint256 _unlockTime) {
        owner = msg.sender;
        recipient = _recipient;
        unlockTime = _unlockTime;
    }

    receive() external payable {}

    function release() external {
        require(msg.sender == owner, "Only owner can release funds");
        require(block.timestamp >= unlockTime, "Funds are locked");

        uint256 amount = address(this).balance;
        require(amount > 0, "No funds to send");

        (bool success, ) = recipient.call{value: amount}("");
        require(success, "Transfer failed");
    }
}

単純にアドレスに保存するだけであれば、mapping(address => Data) accounts;とすれば良さそう。
ただし、この場合は、商品ごとにアドレスを持っていないといけない。
緯度経度やstatusの管理は、フロントエンド側(React)で実装か…
memoryとstorageの仕様詳細が欲しいところ。。。

pragma solidity ^0.8.17;

contract Traceability {

    struct Data {
        uint256 id;
        string name;
        string latitude;
        string longitude;
        string status;
    }

    address[] public users;

    mapping(address => Data) accounts;

    function registerAccount(uint256 _id, string memory _name, string memory latitude, string memory longitude, string memory status)
        public 
        returns (bool)
    {
        accounts[msg.sender].id = _id;
        accounts[msg.sender].name = _name;
        accounts[msg.sender].latitude = latitude;
        accounts[msg.sender].longitude = longitude;
        accounts[msg.sender].status = status;
        
        users.push(msg.sender);
        return true;
    }

    function ViewAccount(address user) public view returns (uint256, string memory, string memory, string memory, string memory) {
        uint256 _id = accounts[user].id;
        string memory _name = accounts[user].name;
        string memory _latitude = accounts[user].latitude;
        string memory _longitude = accounts[user].longitude;
        string memory _status = accounts[user].status;

        return (_id, _name, _latitude, _longitude, _status);
    }

}

ethの受け取り

pragma solidity ^0.8.17;

contract RecvEther {
    address public sender;

    uint public recvEther;

    function () payable {
        sender = msg.sender;
        recvEther += msg.value;
    }
}

memoryは処理中のみ保存し、storageは処理後、ブロックチェーンに保存される。

pragma solidity ^0.8.17;

contract Register {
    struct Data {
        string name;
        uint256 age;
        string hobby;
    }

    // 全ユーザのアドレスを保存
    address[] public users;

    mapping(address => Data) accounts;

    function registerAccount(string memory _name, uint256 _age, string memory _hobby) 
        public 
        returns (bool)
    {
        if (!isUserExist(msg.sender)) {
          users.push(msg.sender);
        }
        // msg.sender はトランザクション送信者
        accounts[msg.sender].name = _name;
        accounts[msg.sender].age = _age;
        accounts[msg.sender].hobby = _hobby;
        return true;
    }

    function isUserExist(address user) public view returns (bool) {
        for (uint256 i = 0; i < users.length; i++) {
            if (users[i] == user) {
                return true;
            }
        }
        return false;
    }

    function ViewAccount(address user) public view returns (string memory, uint256, string memory) {
        string memory _name = accounts[user].name;
        uint256 _age = accounts[user].age;
        string memory _hobby = accounts[user].hobby;

        return (_name, _age, _hobby);
    }
}

remixでデプロイのテストができる

metamaskアカウントでsepoliaにdeployする
https://sepolia.etherscan.io/

フロントエンド

import React from "react";
import Resister from "./Register.json";
import getWeb3 from "./getWeb3";
// import "./App.css";
class App extends React.Component {
  constructor(props) {
    super(props);
    this.state = {
      web3: null,
      accounts: null,
      contract: null,
      name: null,
      age: null,
      hobby: null,
      address: "",
      outputName: null,
      outputAge: null,
      outputHobby: null,
    };
  }

  componentDidMount = async () => {
    try {
      const web3 = await getWeb3();

      const accounts = await web3.eth.getAccounts();
      const networkId = await web3.eth.net.getId();
      const deployedNetwork = Resister.networks[networkId];
      const instance = new web3.eth.Contract(
        Resister.abi,
        deployedNetwork && deployedNetwork.address
      );

      this.setState({ web3, accounts, contract: instance });
    } catch (error) {
      alert(
        `Failed to load web3, accounts, or contract. Check console for details.`
      );
      console.error(error);
    }

    const { accounts } = this.state;
    console.log(accounts);
  };

  // アカウント情報の登録
  writeRecord = async () => {
    const { accounts, contract, name, age, hobby } = this.state;
    const result = await contract.methods.registerAccount(name, age, hobby).send({
      from: accounts[0],
    });
    console.log(result);

    if (result.status === true) {
      alert('会員登録が完了しました。');
    }
  };

  // アカウント情報の読み込み
  viewRecord = async () => {
    const { contract, accounts } = this.state;
    console.log(contract);

    const result = await contract.methods.viewAccount(accounts[0]).call();
    console.log(result);

    const outputName = result[0];
    const outputAge = result[1];
    const outputHobby = result[2];
    this.setState({ outputName, outputAge, outputHobby });
  };

  handleChange = (name) => (event) => {
    this.setState({ [name]: event.target.value });
  };

  render() {
    return (
      <div className="App">
        <br />
        <form>
          <div>
            <label>氏名：</label>
            <input
              onChange={this.handleChange("name")} />
          </div>

          <div>
            <label>年齢：</label>
            <input
              onChange={this.handleChange("age")} />
          </div>

          <div>
            <label>趣味：</label>
            <input
              onChange={this.handleChange("hobby")} />
          </div>

          <button type='button' onClick={this.writeRecord}>
            会員登録
          </button>
        </form>

        <br />
        <br />

        <form>
          <label>検索したいアドレスを入力してください。</label>
          <input onChange={this.handleChange("address")} />

          <button type='button' onClick={this.viewRecord}>
            検索
            </button>
        </form>

        <br />
        <br />

        {this.state.outputName ? <p>氏名: {this.state.outputName}</p> : <p></p>}
        {this.state.outputAge ? <p>年齢: {this.state.outputAge}</p> : <p></p>}
        {this.state.outputHobby ? <p>趣味: {this.state.outputHobby}</p> : <p></p>}

      </div>

    );
  }
}

export default App;

ちょっと記事が古いので期待通りに動かないが、

$ pip3 install eth-brownie
$ npm install -g ganache-cli
$ brownie init
$ tree
.
├── build
│ ├── contracts
│ ├── deployments
│ └── interfaces
├── contracts
├── interfaces
├── reports
├── scripts
└── tests

contract/TokenERC20.sol
https://github.com/PatrickAlphaC/erc20-brownie/tree/main/contracts

pragma solidity ^0.6.0;

interface tokenRecipient { 
    function receiveApproval(address _from, uint256 _value, address _token, bytes calldata _extraData) external; 
}

contract TokenERC20 {
    // Public variables of the token
    string public name;
    string public symbol;
    uint8 public decimals = 18;
    // 18 decimals is the strongly suggested default, avoid changing it
    uint256 public totalSupply;

    // This creates an array with all balances
    mapping (address => uint256) public balanceOf;
    mapping (address => mapping (address => uint256)) public allowance;

    // This generates a public event on the blockchain that will notify clients
    event Transfer(address indexed from, address indexed to, uint256 value);
    
    // This generates a public event on the blockchain that will notify clients
    event Approval(address indexed _owner, address indexed _spender, uint256 _value);

    // This notifies clients about the amount burnt
    event Burn(address indexed from, uint256 value);

    /**
     * Constructor function
     *
     * Initializes contract with initial supply tokens to the creator of the contract
     */
    constructor(
        uint256 initialSupply,
        string memory tokenName,
        string memory tokenSymbol
    ) public {
        totalSupply = initialSupply * 10 ** uint256(decimals);  // Update total supply with the decimal amount
        balanceOf[msg.sender] = totalSupply;                // Give the creator all initial tokens
        name = tokenName;                                   // Set the name for display purposes
        symbol = tokenSymbol;                               // Set the symbol for display purposes
        emit Transfer(address(0), msg.sender, totalSupply);

    }

    /**
     * Internal transfer, only can be called by this contract
     */
    function _transfer(address _from, address _to, uint _value) internal {
        // Prevent transfer to 0x0 address. Use burn() instead
        require(_to != address(0x0));
        // Check if the sender has enough
        require(balanceOf[_from] >= _value);
        // Check for overflows
        require(balanceOf[_to] + _value >= balanceOf[_to]);
        // Save this for an assertion in the future
        uint previousBalances = balanceOf[_from] + balanceOf[_to];
        // Subtract from the sender
        balanceOf[_from] -= _value;
        // Add the same to the recipient
        balanceOf[_to] += _value;
        emit Transfer(_from, _to, _value);
        // Asserts are used to use static analysis to find bugs in your code. They should never fail
        assert(balanceOf[_from] + balanceOf[_to] == previousBalances);
    }

    /**
     * Transfer tokens
     *
     * Send `_value` tokens to `_to` from your account
     *
     * @param _to The address of the recipient
     * @param _value the amount to send
     */
    function transfer(address _to, uint256 _value) public returns (bool success) {
        _transfer(msg.sender, _to, _value);
        return true;
    }

    /**
     * Transfer tokens from other address
     *
     * Send `_value` tokens to `_to` on behalf of `_from`
     *
     * @param _from The address of the sender
     * @param _to The address of the recipient
     * @param _value the amount to send
     */
    function transferFrom(address _from, address _to, uint256 _value) public returns (bool success) {
        require(_value <= allowance[_from][msg.sender]);     // Check allowance
        allowance[_from][msg.sender] -= _value;
        _transfer(_from, _to, _value);
        return true;
    }

    /**
     * Set allowance for other address
     *
     * Allows `_spender` to spend no more than `_value` tokens on your behalf
     *
     * @param _spender The address authorized to spend
     * @param _value the max amount they can spend
     */
    function approve(address _spender, uint256 _value) public
        returns (bool success) {
        allowance[msg.sender][_spender] = _value;
        emit Approval(msg.sender, _spender, _value);
        return true;
    }

    /**
     * Set allowance for other address and notify
     *
     * Allows `_spender` to spend no more than `_value` tokens on your behalf, and then ping the contract about it
     *
     * @param _spender The address authorized to spend
     * @param _value the max amount they can spend
     * @param _extraData some extra information to send to the approved contract
     */
    function approveAndCall(address _spender, uint256 _value, bytes memory _extraData)
        public
        returns (bool success) {
        tokenRecipient spender = tokenRecipient(_spender);
        if (approve(_spender, _value)) {
            spender.receiveApproval(msg.sender, _value, address(this), _extraData);
            return true;
        }
    }

    /**
     * Destroy tokens
     *
     * Remove `_value` tokens from the system irreversibly
     *
     * @param _value the amount of money to burn
     */
    function burn(uint256 _value) public returns (bool success) {
        require(balanceOf[msg.sender] >= _value);   // Check if the sender has enough
        balanceOf[msg.sender] -= _value;            // Subtract from the sender
        totalSupply -= _value;                      // Updates totalSupply
        emit Burn(msg.sender, _value);
        return true;
    }

    /**
     * Destroy tokens from other account
     *
     * Remove `_value` tokens from the system irreversibly on behalf of `_from`.
     *
     * @param _from the address of the sender
     * @param _value the amount of money to burn
     */
    function burnFrom(address _from, uint256 _value) public returns (bool success) {
        require(balanceOf[_from] >= _value);                // Check if the targeted balance is enough
        require(_value <= allowance[_from][msg.sender]);    // Check allowance
        balanceOf[_from] -= _value;                         // Subtract from the targeted balance
        allowance[_from][msg.sender] -= _value;             // Subtract from the sender's allowance
        totalSupply -= _value;                              // Update totalSupply
        emit Burn(_from, _value);
        return true;
    }
}

$ brownie compile
$ ganache-cli
Ganache CLI v6.12.2 (ganache-core: 2.13.2)
(node:179457) [DEP0040] DeprecationWarning: The `punycode` module is deprecated. Please use a userland alternative instead.
(Use `node –trace-deprecation …` to show where the warning was created)

Available Accounts
==================
(0) 0xe866BE96aA793C69dc4CB69D717D12e7b0d5267d (100 ETH)
(1) 0x0696f9fB2fFe037F6E13Deba40912562f97faDC2 (100 ETH)
(2) 0x3785c546Fe6Fc72a7468059d4f7eE6f3d4727F2C (100 ETH)
(3) 0x11165cCc75b3E917C9918C529778c9cE4E58d513 (100 ETH)
(4) 0x3B26Bfe04381231728b9ca3bbC42435aa6D2155e (100 ETH)
(5) 0x9aA0b1bd92d42Da1cA1e842A05Ec5c69F3Dcd123 (100 ETH)
(6) 0x0aC021eCA14d61880693fd6Cd0FAAD598f208778 (100 ETH)
(7) 0xbd07f6ad435698D878f94D9A29337E09c51fd900 (100 ETH)
(8) 0xb8d7f305778207E48A1b70D1D54226ABd76156De (100 ETH)
(9) 0x7e41f77B97d567178A1443E2fe44d3168111BaF6 (100 ETH)

Private Keys
==================
// 省略

HD Wallet
==================
Mnemonic: course acid cereal genuine old blind someone ticket thrive palace napkin time
Base HD Path: m/44’/60’/0’/0/{account_index}

Gas Price
==================
20000000000

Gas Limit
==================
6721975

Call Gas Limit
==================
9007199254740991

Listening on 127.0.0.1:8545

script/deploy_token.py

from brownie import accounts, config, TokenERC20

initial_supply = 1000000000000000000000  # 1000
token_name = "Hpscript"
token_symbol = "HPS"

def main():
    account = accounts.add(config["wallets"]["from_key"])
    erc20 = TokenERC20.deploy(
        initial_supply, token_name, token_symbol, {"from": account} , publish_source=True 
    )

brownie-config.yaml

dependencies:
  - OpenZeppelin/openzeppelin-contracts@3.4.0
compiler:
  solc:
    remappings:
      - '@openzeppelin=OpenZeppelin/openzeppelin-contracts@3.4.0'
dotenv: .env
wallets:
  from_key: ${PRIVATE_KEY}

.env

export WEB3_INFURA_PROJECT_ID=''
export PRIVATE_KEY=''
export ETHERSCAN_TOKEN=''

$ source .env
$ brownie run scripts/deploy_token.py –network sepolia

スマートコントラクトで作るのか… なるほどね〜