4

问题

我希望有一个网站，可以从私人以太坊区块链实时更新用户的财富。

当前解决方案（已损坏）

我为正在挖掘的私有以太坊区块链打开了一个 websocket，我想在前端更新我的 coinbase 余额。我的代码如下：

const express    = require("express");
const Web3       = require("web3");


var app  = express();

app.get("/", (req, res) => res.send("hello world from ping ether application"));
app.get("/ping-ether", function(req, res){


    var web3 = new Web3(new Web3.providers.WebsocketProvider('ws://localhost:8546'));

    var event_newBlockHeaders = web3.eth.subscribe("newBlockHeaders", function(err, result){

        if (err){ 

            console.log(err) 

        } else {

            let acctPromise = web3.eth.getAccounts().then(function(accts){

                let balance = web3.eth.getBalance(accts[0]).then(function(bal){

                    console.log("user: ", accts[0]);
                    console.log("balance: ", bal);

                    res.end("new balance for user: " + bal)

                });

            });
        }

    });


});


// run the server
app.listen(3000, () => console.log("web app listening on port 3000"));

显然，即使最里面的回调不断触发，我也可以在控制台上确认，这并没有在前端实时更新。我想要三件事：

  1. 我应该如何更改此代码，以便前端具有 coinbase 余额的实时代码
  2. 一般来说，代码的嵌套承诺闻起来很糟糕。如何重构它，以便每次导航到时都不必建立 websocket 连接/ping-ether？
  3. 欢迎任何其他建议。我很新node.js
4

2 回答 2

5

未经测试，但这样的事情应该可以工作：

const express    = require("express");
const Web3       = require("web3");

var app  = express();
var web3 = new Web3(new Web3.providers.WebsocketProvider('ws://localhost:8546'));
var balance = -1;

web3.eth.getAccounts().then(accounts => {
  return web3.eth.subscribe("newBlockHeaders", (err, result) => {
    if (err) {
      console.log(err);
    } else {
      web3.eth.getBalance(accounts[0]).then(bal => {
        console.log("user: ", accounts[0]);
        console.log("balance: ", bal);
        balance = bal;
      });
    }
  })
}).then(() => {
  app.listen(3000, () => console.log("web app listening on port 3000"));
});

app.get("/", (req, res) => res.send("hello world from ping ether application"));
app.get("/ping-ether", function (req, res) {
  res.end("new balance for user: " + balance);
});

主要思想是建立一次 websocket 连接和订阅，然后只用当前余额响应传入的 web 请求。我还尝试通过返回订阅承诺来清理嵌套的承诺。

于 2018-01-14T23:21:36.387 回答
2

更新：我最终使用了 websocket，这是解决方案：

import * as Web3     from 'web3'     ; 
import * as express  from 'express'  ;
import * as socketIO from 'socket.io';
import * as http      from 'http'    ;


const CLIENT_PATH = 'path/to/directory'

var app    = express();
var server = http.Server(app);
var io     = socketIO(server);
var web3   = new Web3(new Web3.providers.WebsocketProvider('ws://localhost:8546'));

app.get('/', (req,res) => {
    res.sendFile(CLIENT_PATH + '/index.html');
});


web3.eth.getAccounts().then(accounts => {

    display_account(accounts)
})

function display_account(accounts){

    var user_0 = accounts[0]

    web3.eth.subscribe('newBlockHeaders', (err, ret) => {

        if (err){ 

            console.log("error: ", err)

        } else {

            web3.eth.getBalance(user_0).then(bal => {

                var msg = 'Balance for user ' + user_0 + ' is ' + bal  
                io.emit('message-1', msg)
                console.log('emitted message: ', msg)

            })
        }

    })

}


// use this instead of app.listen
server.listen(3000, () => {

    console.log('listening on 3000')

});

这是 index.html。

<html>
<head></head>

<body>
  <div id="message"></div>

  <script src="/socket.io/socket.io.js"></script>
  <script>

    var socket = io();

    socket.on('message-1', function(msg){
      console.log(msg);
      document.getElementById("message").innerHTML = msg;
    });

  </script>
</body>
</html>
于 2018-01-15T02:18:47.203 回答