Jim's
Tutorials

import web3 from './web3';

const address = '0xeE8b00eA01dA0ee3C38feE826a35095914C27603'
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":"lottery","outputs":[],"payable":false,"stateMutability":"nonpayable","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"}]

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

import Web3 from 'web3';

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

export default web3;

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: '',
    players: [],
    balance: '',
    value: '',
    message: ''
  };

  async componentDidMount(){
    const manager = await lottery.methods.manager().call()
    const players = await lottery.methods.getPlayers().call()
    const balance = await web3.eth.getBalance(lottery.options.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 into the lottery!'})
  }

  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() {
    web3.eth.getAccounts().then(console.log)
    return (
      <div>
        <h2>Lottery Contract</h2>
        <p>
        This contract manager is {this.state.manager}
        There are currently {this.state.players.length} people 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 />
        <h1>{this.state.message}</h1>
        <hr />
        <h4>Ready to pick a winner?</h4>
        <button onClick = {this.onClick}> Pick a Winner</button>
        <hr />
      </div>
    );
  }
}

export default App;

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 returns (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;
    }

 }