1

我想通过 mongoskin 从 mongodb 读取一些数据。但是当我尝试调用 localhost:3000/tasks 时，nodejs 会抛出一个错误

在我的数据库“待办事项”中，“任务”集合中有一些项目。当我启动应用程序时，控制台中的结果工作正常。

谁能看到我在哪里写错了？

错误消息：

500 TypeError: Cannot read property 'tasks' of undefined
at exports.list (/Users/piet/Websites/privat/mongo/routes/tasks.js:7:8) at callbacks     (/Users/piet/Websites/privat/mongo/node_modules/express/lib/router/index.js:164:37)
at param (/Users/piet/Websites/privat/mongo/node_modules/express/lib/router/index.js:138:11)
at pass (/Users/piet/Websites/privat/mongo/node_modules/express/lib/router/index.js:145:5)
at Router._dispatch    (/Users/piet/Websites/privat/mongo/node_modules/express/lib/router/index.js:173:5)
at Object.router   (/Users/piet/Websites/privat/mongo/node_modules/express/lib/router/index.js:33:10)
at next   (/Users/piet/Websites/privat/mongo/node_modules/express/node_modules/connect/lib/proto.js:193:    15)
at Object.methodOverride [as handle]  (/Users/piet/Websites/privat/mongo/node_modules/express/node_modules/connect/lib/middleware/me    thodOverride.js:48:5)
at next (/Users/piet/Websites/privat/mongo/node_modules/express/node_modules/connect/lib/proto.js:193:    15)
at Object.urlencoded [as handle]   (/Users/piet/Websites/privat/mongo/node_modules/express/node_modules/connect/lib/middleware/ur    lencoded.js:49:37)

我的 app.js：

var express = require('express');
var routes = require('./routes');
var tasks = require('./routes/tasks');
var http = require('http');
var path = require('path');

var mongo = require("mongoskin");
var db = mongo.db('localhost:27017/todo?auto_reconnect=true', { 
safe:true })
.collection('tasks')
.find()
.toArray(function(error, items){
    console.log(items);
})

var app = express();
app.set('port', process.env.PORT || 3000);
app.set('views', path.join(__dirname, 'views'));
app.set('view engine', 'jade');
app.use(express.favicon());
app.use(express.logger('dev'));
app.use(express.json());
app.use(express.urlencoded());
app.use(express.methodOverride());
app.use(app.router);
app.use(express.static(path.join(__dirname, 'public')));

if ('development' == app.get('env')) {
   app.use(express.errorHandler());
}
app.get('/', routes.index);
app.get('/tasks', tasks.list);
http.createServer(app).listen(app.get('port'), function(){
  console.log('Express server listening on port ' + app.get('port'));
});

/routes/tasks.js 下的路由文件

exports.list = function(req, res, next){
req.db.tasks.find({
    completed: false
}).toArray(function(error, tasks){
    res.render('tasks', {
        title: "ToDo list",
        name: tasks = tasks || []
    })
})
};
4

3 回答 3

2

您将需要一个中间件来将集合对象连接到您的请求：

var db    = mongo.db('localhost:27017/todo?auto_reconnect=true');
var tasks = db.collection('tasks');
...
app.use(function(req, res, next) {
  req.db = { tasks : tasks }; // this exposes the collection as `req.db.tasks`
                              // to your route handlers
  next();
});
app.use(app.router);
...
于 2013-11-26T10:53:10.023 回答
2

使用 28017 作为端口号。你可以检查你在“req.db”中得到了什么。也许这是未定义的。

于 2013-11-26T09:45:09.673 回答
1

在你的 routes/task.js 中，req 是 Express.js 的请求对象。它没有“db”句柄，这就是您收到错误的原因：

500 TypeError: Cannot read property 'tasks' of undefined

在 app.js 中，这是获取 db 句柄的错误方法：

var mongo = require("mongoskin");
var db = mongo.db('localhost:27017/todo?auto_reconnect=true', { safe:true })
   .collection('tasks')
   .find()
   .toArray(function(error, items){
       console.log(items);
   });

db 代码应该被移动到一个单独的模块中（例如 dbConnection.js），这样每次你需要 db 句柄时，你只需要这样做：

var db = require('./dbConnection').getDb();

routes/task.js 需要获取数据库句柄才能进行数据库调用。所以这里是你修改后的 app.js、routes/task.js 和新的 dbConnection.js 文件：

dbConnection.js：

var open = function() {
    return require('mongoskin').db('localhost:27017/todo?auto_reconnect=true',
        {safe: true, strict: false}
    );
};

var db = open();

var dbConnection = {
    getDb: function() {
        if (!db) {
           db = open();
        }
        return db;
    }
};

module.exports = dbConnection;

路线/task.js：

var db = require('../dbConnection').getDb();

exports.list = function(req, res, next){
    var tasksCollection = db.collection('tasks');

    tasksCollection.find({ completed: false }).toArray(function(error, tasks){
        res.render('tasks', {
            title: "ToDo list",
            name: (tasks || [])
        });
    });
};

应用程序.js：

var express = require('express');
var routes = require('./routes');
var tasks = require('./routes/tasks');
var http = require('http');
var path = require('path');

var app = express();
app.set('port', process.env.PORT || 3000);
app.set('views', path.join(__dirname, 'views'));
app.set('view engine', 'jade');
app.use(express.favicon());
app.use(express.logger('dev'));
app.use(express.json());
app.use(express.urlencoded());
app.use(express.methodOverride());
app.use(app.router);
app.use(express.static(path.join(__dirname, 'public')));

if ('development' == app.get('env')) {
    app.use(express.errorHandler());
}
app.get('/', routes.index);
app.get('/tasks', tasks.list);
http.createServer(app).listen(app.get('port'), function(){
    console.log('Express server listening on port ' + app.get('port'));
});
于 2013-11-26T11:34:18.353 回答