是否可以在 Node.js 中监听对象实例化?

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问题描述

我正在 Node.Js 中开发一个浏览器游戏，我有这个脚本:

game.js >>

var config = require('./game_config.js');var mysql = require('mysql');var app = require('express')();var http = require('http').Server(app);var io = require('socket.io')(http);var connexion = mysql.createConnection({主机":config.DB_HOST，'用户':config.DB_USER，'密码':config.DB_PASS，数据库":config.DB_NAME});var Player = require('./server/class.player.js');io.on('connect', function(socket) {console.log('Co');播放器socket.on('登录', 函数(数据) {connexion.query("SELECT * FROM player WHERE nick = '"+data.login+"' AND pass = '"+data.pass+"'", function(err, rows) {如果(错误){抛出错误；} 别的 {如果(行.长度== 0){var dataRet = "LOG";socket.emit('登录', dataRet);} 别的 {var p = 行[0];var dataRet = new Player(p.id, p.nick, p.map_id, p.x, p.y, connexion).toJson();控制台日志(dataRet)；}//没有 setTimeout 它将无法工作，因为对象没有时间实例化设置超时(功能(){socket.emit('登录', dataRet);},1000);}});});socket.on('disconnect', function(socket) {console.log('Disco');});});

class.Player.js >>

var Player = function (id, name, map_id, x, y, connexion) {this.id = id;this.name = 名称；this.map_id = map_id ;this.x = x;这.y = y;this.link = 连接；this.toJson = 函数 () {返回 {'id' : this.id,'name' : this.name,'map_id' : this.map_id,'x' : this.x,'y' : this.y};}}module.exports = 用户；

所以基本上，由于 game.js 中的setTimeout()"(用于 socket.emit() 事件)，我的代码运行良好.如果我不使用它，由于 Node.js 的异步性，对象 'dataRet' 没有时间实例化，因此套接字发出未定义"或空".

所以我在想，必须有一种方法来侦听对象实例化，以便在完成后立即通过 socket.io 发出它.

解决方案

警告:SQL 注入漏洞

这与您的问题本身无关，但这很重要-您有一个巨大的SQL 注入漏洞，任何人都可以对您的数据库进行任何操作.

代替:

connection.query(SELECT * FROM player WHERE nick = '"+ data.login + "' AND pass = '" + data.pass + "'",函数(错误，行){//...});

要么使用:

connection.escape(data.login) 和 connection.escape(data.pass) 代替 data.login 和 >data.pass

或:

connection.query("SELECT * FROM player WHERE nick = ? AND pass = ?", [data.login, data.pass],函数(错误，行){//...});

它不仅更安全，而且实际上更易于阅读和理解.请参阅:转义查询值/github.com/felixge/node-mysql#readme" rel="nofollow noreferrer">node-mysql 手册.

答案

现在，回到你的问题.您的 Player 构造函数没有任何异步内容，因此您的问题一定是其他问题.奇怪的是，您的 Player.js 导出 User(未定义)而不是 Player(已定义)，所以我很惊讶它甚至可以工作.或者，您发布的代码可能与您实际使用的代码不同，这可以解释为什么您存在代码中不明显的竞争条件.

但是如果您的 Player 构造函数进行了一些异步调用，那么我建议添加一个回调参数并从构造函数中调用它:

var Player = function (id, name, map_id, x, y, connexion, callback) {this.id = id;this.name = 名称；this.map_id = map_id ;this.x = x;这.y = y;this.link = 连接；this.toJson = 函数 () {返回 {'id' : this.id,'name' : this.name,'map_id' : this.map_id,'x' : this.x,'y' : this.y};}//一些你必须等待的异步调用//用 setTimeout 符号化:setTimeout(function () {if (callback && typeof callback === 'function') {回调(这个)；}}, 1000);}

然后您可以将回调传递给您的构造函数，因此:

 } else {var p = 行[0];var dataRet = new Player(p.id, p.nick, p.map_id, p.x, p.y, connexion).toJson();控制台日志(dataRet)；}//没有 setTimeout 它将无法工作，因为对象没有时间实例化设置超时(功能(){socket.emit('登录', dataRet);},1000);

可以更改为:

 } else {var p = 行[0];var dataRet = new Player(p.id, p.nick, p.map_id, p.x, p.y, connexion, function () {socket.emit('登录', dataRet);}).toJson();控制台日志(dataRet)；}

但在这里，正如我所说，没有什么是异步的，而且你的 dataRet 甚至在你运行 setTimeout 之前就已经设置好了，所以这并没有解决你的问题，但它正在回答你的问题.>

I am working on a browser-game in Node.Js and I have this script :

var config = require('./game_config.js');
var mysql = require('mysql');
var app = require('express')();
var http = require('http').Server(app);
var io = require('socket.io')(http);
var connexion = mysql.createConnection({
    'host': config.DB_HOST,
    'user' : config.DB_USER,
    'password' : config.DB_PASS,
    'database' : config.DB_NAME
});
var Player = require('./server/class.player.js');

io.on('connect', function(socket) {
    console.log('Co');
    var player
    socket.on('login', function(data) {
        connexion.query("SELECT * FROM player WHERE nick = '"+data.login+"' AND pass = '"+data.pass+"'", function(err, rows) {
            if (err) {
                throw err;
            } else {
                if (rows.length == 0) {
                    var dataRet = "LOG";
                    socket.emit('login', dataRet);
                } else {
                    var p = rows[0];
                    var dataRet = new Player(p.id, p.nick, p.map_id, p.x, p.y, connexion).toJson();
                    console.log(dataRet);
                }
                // Without setTimeout it wouldn't work because the object didn't have the time to instantiate
                setTimeout(function() {
                    socket.emit('login', dataRet);
                },1000);
            }
        });
    });
    socket.on('disconnect', function(socket) {
        console.log('Disco');
    });
});

var Player = function (id, name, map_id, x, y, connexion) {
    this.id = id;
    this.name = name;
    this.map_id = map_id ;
    this.x = x;
    this.y = y;
    this.link = connexion;
    this.toJson = function () {
        return {
            'id' : this.id,
            'name' : this.name,
            'map_id' : this.map_id,
            'x' : this.x,
            'y' : this.y
        };
    }
}

module.exports = User;

So basicly, my code works fine thanks to the "setTimeout()" in game.js (for the socket.emit() event). If I don't use it, the object 'dataRet' doesn't have the time to instantiate due to the asynchronousity of Node.js, so the socket emits "undefined" or "null".

So I was thinking, there MUST be a way to listen for an object instantiation in order to emit it through socket.io as soon as it's done.

解决方案

Warning: SQL Injection Vulnerability

This is not related your question per se but this is quite important - you have a huge SQL injection vulnerability and anyone can do anything to your database.

Instead of:

connection.query(
  "SELECT * FROM player WHERE nick = '"
  + data.login + "' AND pass = '" + data.pass + "'",
  function (err, rows) {
    //...
  }
);

either use:

connection.escape(data.login) and connection.escape(data.pass) in place of data.login and data.pass

or:

connection.query(
  "SELECT * FROM player WHERE nick = ? AND pass = ?", [data.login, data.pass],
  function (err, rows) {
    // ...
  }
);

It is not only safer but also actually much easier to read and understand. See: Escaping query values in node-mysql manual.

The Answer

Now, back to your question. There is nothing asynchronous about your Player constructor so your problem must be something else. What is strange here us that your Player.js exports User (that is not defined) and not Player (that is defined) so I'm surprised it even works at all. Or you maybe posted a different code than what you're actually using which would explain why you have a race condition that is not obvious from the code.

But if your Player constructor was making some asynchronous calls then I would suggest adding a callback argument and calling it from the constructor:

var Player = function (id, name, map_id, x, y, connexion, callback) {
    this.id = id;
    this.name = name;
    this.map_id = map_id ;
    this.x = x;
    this.y = y;
    this.link = connexion;
    this.toJson = function () {
        return {
            'id' : this.id,
            'name' : this.name,
            'map_id' : this.map_id,
            'x' : this.x,
            'y' : this.y
        };
    }

    // some async call that you have to wait for
    // symbolized with setTimeout:
    setTimeout(function () {
      if (callback && typeof callback === 'function') {
        callback(this);
      }
    }, 1000);
}

and then you can pass a callback to your constructor, so this:

          } else {
                var p = rows[0];
                var dataRet = new Player(p.id, p.nick, p.map_id, p.x, p.y, connexion).toJson();
                console.log(dataRet);
            }
            // Without setTimeout it wouldn't work because the object didn't have the time to instantiate
            setTimeout(function() {
                socket.emit('login', dataRet);
            },1000);

could change to something like:

          } else {
                var p = rows[0];
                var dataRet = new Player(p.id, p.nick, p.map_id, p.x, p.y, connexion, function () {
                    socket.emit('login', dataRet);
                }).toJson();
                console.log(dataRet);
            }

but here, as I said, nothing is asynchronous and also your dataRet is already set even before you run the setTimeout so this is not solving your problem, but it is answering your question.

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