ソフトウェアエンジニアの技術ブログ：Software engineer tech blog

$ sudo npm install -g create-react-app
$ create-react-app lottery-react
$ cd lottery-react
$ npm run start

http://192.168.34.10:3000/

$ sudo npm install -g yarn
$ yarn -v
1.22.5
$ npm install –save web3@1.0.0-beta.26

$ cd ..
$ mkdir lottery
$ cd lottery
$ sudo npm install solc@0.4.17
$ npm install –save mocha ganache-cli web3@1.0.0-beta.26
$ npm install –save truffle-hdwallet-provider@0.0.3

contract/Lottery.sol

pragma solidity ^0.4.17;

contract Lottery {
	address public manager;
	address[] public players;

	function Lottery () public {
		manager = msg.sender;
	}

	function enter() public payable {
		require(msg.value > .01 ether);

		players.push(msg.sender);
	}

	function random() private view return (uint) {
		return uint(keccak256(block.difficulty, now, players));
	}

	function pickWinner() public restricted {
		uint index = random() % players.length;
		players[index].transfer(this.balance);
		players = new address[](0);
	}

	modifier restricted() {
		require(msg.sender == manager);
		_;
	}

	function getPlayers() public view returns(address[]){
		return players;
	}
}

compiler.js

const path = require('path');
const fs = require('fs');
const solc = require('solc');

const IndexPath = path.resolve(__dirname,'contracts', 'Lottery.sol');
const source = fs.readFileSync(IndexPath, 'utf8');

console.log(solc.compile(source,1));

ABIとは、Application Binary Interface

lottery.js

import web3 from './web3';

const address = '0xaC24CD668b4A6d2935b09596F1558c1E305F62F1';


const abi = [{
    "constant": true,
    "inputs": [],
    "name": "manager",
    "outputs": [{
        "name": "",
        "type": "address"
    }],
    "payable": false,
    "stateMutability": "view",
    "type": "function"
}, {
    "constant": false,
    "inputs": [],
    "name": "pickWinner",
    "outputs": [],
    "payable": false,
    "stateMutability": "nonpayable",
    "type": "function"
}, {
    "constant": true,
    "inputs": [],
    "name": "getPlayers",
    "outputs": [{
        "name": "",
        "type": "address[]"
    }],
    "payable": false,
    "stateMutability": "view",
    "type": "function"
}, {
    "constant": false,
    "inputs": [],
    "name": "enter",
    "outputs": [],
    "payable": true,
    "stateMutability": "payable",
    "type": "function"
}, {
    "constant": true,
    "inputs": [{
        "name": "",
        "type": "uint256"
    }],
    "name": "players",
    "outputs": [{
        "name": "",
        "type": "address"
    }],
    "payable": false,
    "stateMutability": "view",
    "type": "function"
}, {
    "inputs": [],
    "payable": false,
    "stateMutability": "nonpayable",
    "type": "constructor"
}];


export default new web3.eth.Contract(abi, address);

web3.js

import Web3 from 'web3';

const web3 = new Web3(window.web3.currentProvider);

export default web3;

App.js

import React, { Component } from 'react';
import logo from './logo.svg';
import './App.css';
import web3 from './web3';
import lottery from './lottery';

class App extends Component {
  state = {
    manager: '',
    player: [],
    balance: '',
    value: '',
    messaget: ''
  };

  async componentDidMount() {
    const manager = await lottery.methods.manager().call();
    const players = await lottery.methods.getPlayers().call();
    const balance = await web3.eth.getBalance(lottery.opetions.address);

    this.setState({manager, players, balance});
  }

  onSubmit = async(event) => {
    event.preventDefault();

    const accounts = await web3.eth.getAccounts();

    this.setState({message: 'Waiting on transaction success...'});

    await lottery.methods.enter().send({
      from: accounts[0],
      value: web3.utils.toWei(this.state.value, 'ether')
    });

    this.setState({message: 'you have been entered!'});
  };

  onClick = async() => {
    const accounts = await web3.eth.getAccounts();

    this.setState({message: "waiting on transaction success..."});

    await lottery.methods.pickWinner().send({
      from: accounts[0]
    });

    this.setState({message: 'A winner has been picked'});
  };

  render() {
    return (
    <div>
      <h2>Lottery Contract</h2>
      <p>
        This contract is managed by {this.state.manager}.
        There are currently {this.state.players.length} peple entered,
        competing to win {web3.utils.fromWei(this.state.balance, 'ether')}
      </p>
      <hr />

        <form onSubmit={this.onSubmit}>
            <h4>Want to try your luck?</h4>
            <div>
              <label>Amount of ether to enter</label>
              <input
              value = {this.state.value}
                onChange={event => this.setState({ value: event.target.value })}
              />
            </div>
            <button>Enter</button>
        </form>

        <hr />

        <h4>Ready to pick a winner?</h4>
        <button onClick={this.onClick}>Pick a winner!</button>

        <hr />
        <h1>{this.state.message}</h1>
      </div>
  );
  }
}

export default App;

なるほど、全体の流れはわかった