以太坊DAPP[3]-博彩-react特性与博彩合约实例

博彩实例

在之前的课程中，我们介绍了如何编译与部署合约。现在，我们假设已经把合约部署到了ropsten的网络之上。得到了地址。
现在，我们需要通过合约的ABI接口与地址来构建博彩合约的实例。

新建文件：src/lottery.js:

import web3 from './web3';
const address = '0x94A261B507c4388f2ADcFfaA5685ffdF53ebcba5';

const abi = [{"constant":true,"inputs":[],"name":"manager","outputs":[{"name":"","type":"address"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":false,"inputs":[],"name":"getPlayers","outputs":[{"name":"","type":"address[]"}],"payable":false,"stateMutability":"nonpayable","type":"function"},{"constant":false,"inputs":[],"name":"enetr","outputs":[],"payable":true,"stateMutability":"payable","type":"function"},{"constant":false,"inputs":[],"name":"pickwiner","outputs":[],"payable":false,"stateMutability":"nonpayable","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);

src/App.js:
componentDidMount为react class的生命周期函数，其在reander之后执行。state是react中特殊的属性，其只是存在于class component中，用于存储属性。
当state中的状态变化之后，都会重新的执行reander函数，从而让页面展现出不同的效果。下面获取了管理者的地址并存储在了state状态变量中。在页面中显示了管理者的地址。

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:'',
   }

  async componentDidMount(){
      const manager = await lottery.methods.manager().call();
        this.setState({manager});
  }


  render() {
    return (
      <div>
        <h1>lottery管理者地址：</h1>
        <p>this is manager by  {this.state.manager}</p>
      </div>
    );
  }
}
export default App;