TypeError:无法调用未定义的方法"get"

TypeError:无法调用未定义的方法

问题描述：

我尝试使用express.js在node.js上创建一个简单的CRUD应用程序.我尝试连接到DB，但是出现错误TypeError: Cannot call method 'get' of undefined.我的部分代码:

I try to make a simple CRUD application on node.js using express.js. I try to connect to DB, but I have an error TypeError: Cannot call method 'get' of undefined. Part of my code:

app.js

var mongo = require('mongodb');
var monk = require('monk');
var db = monk('localhost:27017/notepad');

var app = express();

app.get('/users', routes.userlist);

// mongoDB
app.use(function (req, res, next) {
   req.db = db; // this is setting up db property to request
   next();
});

routes/index.js

exports.userlist = function (req, res) {
var db = req.db;
var collection = db.get('usercollection'); // error in this line
collection.find({}, {}, function (e, docs) {
    res.render('userList', {
        "userlist": docs
    });
});
};

我认为数据库的实例未设置或在其他文件中不可用.该如何解决?

I think the instanse of DB is not setted or it's not available in other file. How to solve this?

答

您的app.use应该写在app.get之前. app.get首先由Express调用.

Your app.use should be written before your app.get. The app.get is called first by Express.

var mongo = require('mongodb');
var monk = require('monk');
var db = monk('localhost:27017/notepad');

var app = express();

// mongoDB
// Do all your "pre-route" use() functions first
app.use(function (req, res, next) {
   req.locals.db = db; // this is setting up db property to request
   next();
});

app.get('/users', routes.userlist);

在您的路线上...

var db = req.locals.db; // Instead of req.db

甚至更好...

var mongo = require('mongodb');
var monk = require('monk');
var db = monk('localhost:27017/notepad');

var app = express();

app.locals.db = db;

app.get('/users', routes.userlist); // Access it using req.locals.db

TypeError:无法调用未定义的方法"get"

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