小编Eri*_*uez的帖子

我从action-struts 2获得数据json抛出ajax的观点。一些数据集的数据。

例

{"home":"1234","room": null}.

我可以读取data.home，并且得到1234的值，但是当我尝试读取时data.room，我在浏览器的控制台中遇到了Uncaught错误，如何处理此Uncaught错误...

我的问题是：当我创建一个与默认用户不同的 PostgreSQL 用户时postgres，我是否还应该创建一个新数据库供该用户连接？

这样的设置有什么意义呢？

我正在用 React 构建一个简单的应用程序，但是var manager = wait lottery.methods.manager().call(); 永远不会检索值，我怎么会错呢？

彩票.js

import web3 from './web3';

const address = '0x430b45dcf781d58e73CeeA288b4196B6ddeE4d7E';

const abi = [{"inputs":[],"stateMutability":"nonpayable","type":"constructor"},{"inputs":[],"name":"enter","outputs":[],"stateMutability":"payable","type":"function"},{"inputs":[],"name":"getPlayers","outputs":[{"internalType":"address[]","name":"","type":"address[]"}],"stateMutability":"view","type":"function"},{"inputs":[],"name":"manager","outputs":[{"internalType":"address","name":"","type":"address"}],"stateMutability":"view","type":"function"},{"inputs":[],"name":"pickWinner","outputs":[],"stateMutability":"nonpayable","type":"function"},{"inputs":[{"internalType":"uint256","name":"","type":"uint256"}],"name":"players","outputs":[{"internalType":"address","name":"","type":"address"}],"stateMutability":"view","type":"function"},{"inputs":[],"name":"random","outputs":[{"internalType":"uint256","name":"","type":"uint256"}],"stateMutability":"view","type":"function"}];
const cont = new web3.eth.Contract(abi,address);
export default cont;

应用程序.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 {
  
  constructor (props){
    super(props);
    this.state = {"manager":''};
  }

  async componentDidMount(){
    console.log("componentDidMount fired");
    var manager = await lottery.methods.manager().call();//never set  manager var
    this.setState({manager});
  }

  render() {
    return (
      <div> …