问题描述
我正在使用node.js/express，并且我有一个Mongodb来存储一些数据集.用户可以在网页上输入，编辑和删除数据(一切正常).例如，要添加数据，我具有以下代码:
I'm using node.js/express and I have a Mongodb to store some sets of data. On a webpage the user can enter, edit and delete data (which all works fine). For example, to add data I have the following code:
router.post('/addset', function(req,res) {
var db = req.db;
var collection = db.get('paramlist');
collection.insert(req.body, function(err, result){
res.send(
(err === null) ? { msg: '' } : { msg: err }
);
});
});
在我的app.js文件中，包括以下行
In my app.js file I include the lines
// Database
var mongo = require('mongodb');
var monk = require('monk');
var db = monk('localhost:27017/paramSet1');
以及
app.use(function(req,res,next){
req.db = db;
next();
});
使数据库在其余代码中可访问(遵循本教程: http://cwbuecheler.com/web/tutorials/2013/node-express-mongo/，我是这些方面的初学者).
to make the database accessible in the rest of the code (following this tutorial: http://cwbuecheler.com/web/tutorials/2013/node-express-mongo/ , I'm a beginner with these things).
因此，所有这些工作正常.我的问题如下:我想添加一个测试，如果数据库中已经存在具有相同名称的数据集，并向用户发送消息.遵循此答案如何查询MongoDB以测试项目是否存在吗?我尝试使用collection.find.limit(1).size()，但出现错误
So all this works fine. My problem is the following: I would like to add a test if a dataset with the same name is already in the database and give a message to the user. Following this answer How to query MongoDB to test if an item exists? I tried using collection.find.limit(1).size() but I get the error
undefined is not a function
我尝试了以下操作.在上述费用(router.post)中，我尝试在行var集合之后添加...
I tried the following things. In the cost above (router.post) I tried adding after the line var collection...
var findValue = collection.find({name:req.body.name});
如果我随后执行console.log(findValue)，我将得到一个巨大的输出JSON.然后，我尝试了console.log(findValue.next())，但遇到相同的错误(未定义不是函数).我也尝试过
If i then do console.log(findValue), I get a huge output JSON. I then tried console.log(findValue.next()) but I get the same error (undefined is not a function). I also tried
collection.find({name:req.body.name}).limit(1)
以及
collection.find({name:req.body.name}).limit(1).size()
，但也会收到此错误.因此，总而言之，collection.insert，collection.update和collection.remove都可以工作，但find()不能.另一方面，当我进入mongo shell时，该命令运行正常.
but also get this error. So in summary, collection.insert, collection.update and collection.remove all work, but find() does not. On the other hand, when I enter the mongo shell, the command works fine.
对于任何提示和想法，我将不胜感激.
I would be grateful for any hints and ideas.
console.log(findValue)的输出是:
The output to console.log(findValue) is:
{ col:
{ manager:
{ driver: [Object],
helper: [Object],
collections: [Object],
options: [Object],
_events: {} },
driver:
{ _construct_args: [],
_native: [Object],
_emitter: [Object],
_state: 2,
_connect_args: [Object] },
helper: { toObjectID: [Function], isObjectID: [Function], id: [Object] },
name: 'paramlist',
col:
{ _construct_args: [],
_native: [Object],
_emitter: [Object],
_state: 2,
_skin_db: [Object],
_collection_args: [Object],
id: [Object],
emitter: [Object] },
options: {} },
type: 'find',
opts: { fields: {}, safe: true },
domain: null,
_events: { error: [Function], success: [Function] },
_maxListeners: undefined,
emitted: {},
ended: false,
success: [Function],
error: [Function],
complete: [Function],
resolve: [Function],
fulfill: [Function],
reject: [Function],
query: { name: 'TestSet1' } }
推荐答案
find返回光标，而不是匹配的文档本身.但更适合您的情况是使用 :
find returns a cursor, not the matching documents themselves. But a better fit for your case would be to use findOne:
collection.findOne({name:req.body.name}, function(err, doc) {
if (doc) {
// A doc with the same name already exists
}
});
这篇关于node.js:当collection.insert工作时，Mongodb db.collection.find()无法正常工作的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！