I am trying to create a todo list, where i am using mlab as my db provider.
tasks = db.connect().collection('tasks');
tasks.find().toArray(function (err, result) {
console.log("result", result) // giving me result
if(err) throw err;
res.render('tasks/index', {title:"Tasks",tasks:result});
})
Attached is one single shot of all routes output in console.
In the image (1) is the output of find().toArray()
(2) is get update and i am getting the id of task in the url route params.
(3) is after i run this findOne statment.
update function -> get task based on id
tasks.findOne({"_id":"59c91fbb4b262004f059f67f"}, function(err, task){
console.log(err)
console.log(task)
res.render('tasks/update', {title:"Update"});
});
I am getting null as value.(Note: I am hard coding the value for confirmation).
Let me know why i am getting null as the id matches (which you can refer from 1).
Task-2
Also, if i want to update, how shuld i send the altered values.
Regarding your first question, when matching on _id with Mongo you need to define your search criteria as an ObjectId :
tasks.findOne({"_id":ObjectId("59c91fbb4b262004f059f67f")}, function(err, task){
console.log(err)
console.log(task)
res.render('tasks/update', {title:"Update"});
});
Regarding the update, are you having some kind of trouble in particular ? The documentation has plenty of information regarding the structure of the query you're supposed to send :)
Related
I am developing an application in Express with Mongo, in which i have to query, whether a document exits in the collection or not. I am doing this:
var dept= req.body.dept;
var name= req.body.name;
mongoose.model('User').find({'dept': dept, 'name': name}, function(err, user){
if(err){
res.render('user/test1');
}else{
res.redirect('/');
}
});
What I want to do is to check if that document exits in the collection and upon true condition, i want to redirect to another page otherwise render the current page. But when I pass the wrong input, even then it goes to the else part and redirects it.
Well you are actually using mongoose, so there is in fact a distinction between what is returned by this specific version ( abtraction ) to what the base driver itself returns.
In the case of mongoose, what is returned is either an array of results or a null value if nothing is found. If you are looking for a singular match then you probably really want findOne() instead of a result array.
But of course the case would be a null result with either function if not returned as opposed to an err result that is not null, which is of course about specific database connection errors rather than simply that nothing was found.
The base driver on the other hand would return a "Cursor" ( or optionally considered a promise ) instead, which can either be iterated or converted to an array like mongoose does via the .toArray() method. The .findOne() method of the base driver similarly returns either a result or a null document where the conditions do not match.
mongoose.model('User').findOne({'dept': dept, 'name': name}, function(err, user){
if(err){
// if an error was actually returned
} else if ( !user ) {
// Nothing matched, in REST you would 404
} else {
// this is okay
}
});
In short, if you want to test that you actually found something, then look at the user value for a value that is not null in order to determine it matched. If it is null then nothing was matched.
So no match is not an "error", and an "error" is in fact a different thing.
Is there a save operation in mongoose.js or mongodb api, which returns the _id of stored entry?
In mongoose the following will save the Entry.
p.save(function (err) {
if (err) return handleError(err);
else console.log('saved');
})
})
Likewise db.collection.save(document) will save document in mongodb api. But in both cases, you need to query db again for _id, which I want to avoid. As it seems ineffient.
When you instantiate an object in Mongoose, the object will have an _id already assigned (as it's assigned on the client by default).
So, if you just check:
console.log(p.id);
You'll see that it has a value before you call save.
And in the case of using the native driver for Node.JS, the document is returned in the result parameter with the _id set.
var collection = db.collection("tests");
collection.insert(p, function(err, results) {
if (err) { return; }
// results in an array, and in this case
// results[0]._id would be available
});
Short Version: I basically want to do what show collections does in the mongo shell, in mongoose.
Long Version:
I want to create an application that allows users to basically create their own Schema's > Collections > Documents using mongo + mongoose + node.js.
The first step of this application would be to show previously created Collections and their Documents. But since these would be created by a user their names are not known.
The code I've found that came closest was:
function find (collec, query, callback) {
mongoose.connection.db.collection(collec, function (err, collection) {
collection.find(query).toArray(callback);
});
}
But I don't know what the name of the collection is so I can't pass the 'collec' parameter.
So, anyone know how to get the list of collections without knowing their names?
I ended up using node-mongodb-native (the mongo driver that mongoose works on top of) to get the collection names:
var nmn_connect = require('mongoose/node_modules/mongodb').connect;
nmn_connect('mongo://localhost:27017/DATABASE', function(err, db) {
if(!err){
db.collectionNames(function(err, names){ // what I was looking for
if(!err){
console.log(names);
db.close();
}else{
console.log(err);
db.close();
}
});
}else{
console.log(err)
}
});
The Object returned by mongoose.connect() has no method similar to collectionNames() that I can find.
I know nothing of mongoose, but this page suggests that you could use mongoose.connection.collections to access all collections: http://mongoosejs.com/docs/api.html
each collection again should have a name attribute.
try this:
mongoose.connection.db.collectionNames(function (err, names) {
});
I'm trying to 'stream' data from a node.js/MongoDB instance to the client using websockets. It is all working well.
But how to I identify the last document in the result? I'm using node-mongodb-native to connect to MongoDB from node.js.
A simplified example:
collection.find({}, {}, function(err, cursor) {
if (err) sys.puts(err.message);
cursor.each(function(err, doc) {
client.send(doc);
});
});
Since mongodb objectId contatins creation date you can sort by id, descending and then use limit(1):
db.collection.find().sort( { _id : -1 } ).limit(1);
Note: i am not familiar with node.js at all, above command is mongo shell command and i suppose you can easy rewrite it to node.js.
Say I have companies collection. Below snippet gives me last document in the collection.
db.companies.find({},{"_id":1}).skip(db.companies.find().count()-1);
Code cannot rely on _id as it may not be on a specific pattern always if it's a user defined value.
Use sort and limit, if you want to use cursor :
var last = null;
var findCursor = collection.find({}).cursor();
findCursor.on("data", function(data) {
last = data;
...
});
findCursor.on("end", function(data) {
// last result in last
....
});
For this app, I'm using Node.js, MongoDB, Mongoose & Express
So I have a Param Object that contains an array of Pivots, and I want to read certain data from the pivots as outlined below
---in models.js-------------------------
var Pivot = new Schema({
value : String
, destination : String
, counter : Number
});
var Param = new Schema({
title : String
, desc : String
, pivots : [Pivot]
});
------------- in main.js --------------
var Param = db.model('Param');
app.get('/:title/:value', function(req, res){
Param.findOne({"title":req.param('title')}, function(err, record){
console.log(record.pivots);
record.pivots.find({"value":req.param('value')}, function(err, m_pivot){
pivot.counter++;
res.redirect(m_pivot.destination);
});
record.save();
});
});
I know that the code works until console.log(record.pivots), since i got a doc collection with the right pivot documents inside.
However, there does not seem to be a find method to let me match an embedded document by the 'value' property defined in the schema. Is it possible to search through this array of embedded documents using .find() or .findOne() , and if not, is there some easy way to access it through mongoose?
varunsrin,
This should do it
app.get('/:title/:value', function(req, res) {
Param.findOne({'pivots.value': req.param('value'), "title":req.param('title')}},
function(err, record) {
record.pivot.counter++;
res.redirect(m_pivot.destination);
record.save();
});
});
Note the pluralization of the query to match the field name in your schema
You can querying using embedded document properties like this:
{'pivot.value': req.param('value')}}
Update in response to comment:
app.get('/:title/:value', function(req, res) {
Param.findOne({'pivot.value': req.param('value'), "title":req.param('title')}},
function(err, record) {
record.pivot.counter++;
res.redirect(m_pivot.destination);
record.save();
});
});
I solved it temporarily using a simple for loop to parse the object array as follows:
for (var i=0; i <record.pivots.length; i++){
if (record.pivots[i].value == req.param('value')){
res.redirect(record.pivots.destination);
}
}
However, I still think that Mongoose must have a simpler way of interacting with embedded documents - and this loop is somewhat slow, especially when the number of embedded documents grows large.
If anyone has any suggestions for a faster way to search this object array either in js or with a mongoose function, please post below.
the biggest problem with this is that if your req has some fields empty (that should act as wildcard), you will not find anything since mongo tries to match empty params as well, so searching for {"user":"bob", "color":""} is not the same as {"user":"bob", "color":"red"} or {"user":"bob"}. this means that you have to first create a query object and filter out any unused parameters before you pass it in, and if you create a query object, you can no longer do something like "user.name=..." because mongo interperets this as an error since it does not first resolve the object literal into a string.
Any ideas on this problem?
ps. You'd think it would be easy enough to make an object like:
user.name="bob"; user.color:"green"; user.signup.time="12342561"
and then just use user as a query object :/
I think you are looking for the "$in" keyword?
As in:
{a: {$in: [10, "hello"]}}
source: MongoDB Queries CheatSheet