Alright, so I have a collection called Polls. Inside the Polls "table" there is an attribute called choiceObjects which is an array of objects. Each object inside this array has its own attributes. What I need to do is update one of the attributes there. Ill give you a screen shot so you can better visualise what Im talking about
As you can see the choice objects have attributes like body, country etc. There is another attribute called pollid which is set to optional and therefore you cant see it right now. I need to update this pollid attribute now that I have acess to the pollid
Polls.update(
{ _id: pollId },
{ "$set": { "choiceObjects": { pollid: pollId } } }
); //this is kind of what Im trying to do but this isnt right
Since then... I have further tried the following :
var selectedpoll = Polls.findOne(pollId);
console.log(selectedpoll);
//Polls.update( selectedpoll, {"$set"{'choiceObjects.$.pollId':pollId}},false, true );
but when i try that i get the error : the positional operator did not find the match needed from the query. unexpanded update: choiceObjects.$.pollId
If I understand your objective correctly, you want to update (or add) pollid to all objects in the choiceObjects array. Unfortunately $, $push, $addToSet only work with single elements AFAIK.
This might not be what you are looking for but one possible and very obvious way to approach this problem would be to update the entire array in the collection i.e.
var choiceObjects = Polls.findOne({_id: pollId}).choiceObjects;
for (var i = 0; i < choiceObjects.length; i++) {
choiceObjects[i].pollid = pollid;
}
Polls.update({_id: pollid}, {choiceObjects: choiceObjects});
Related
I have a rather complex MongoDB Operator that uses a where to look through multiple users to see if they have a certain value, and if so it changes the value of it. My problem is that the value it checks for can be different for different cases, so my $set would require me to add strings together to get the property that I would change. This is what I mean:
users.update({$where:function() {
return this.profile.chatInfo.subscribedRooms.hasOwnProperty(findChatroom._id);
}},{$set: {"profile.chatInfo.subscribedRooms."+findChatroom._id:false}},{multi:true}
)
The only thing that does not work in that code is the part in the $set where I add "profile.chatInfo.subscribedRooms."+findChatroom._id
Another thing I have tried was making a variable that was equal to those strings added, and use the variable, but it also didn't work.
var addedString = "profile.chatInfo.subscribedRooms."+findChatroom._id;
users.update({$where:function() {
return this.profile.chatInfo.subscribedRooms.hasOwnProperty(findChatroom._id);
}},{$set: {addedString:false}},{multi:true}
)
What I am actually trying to do here, is that whenever a chat message is sent, this operator is ran. It looks for every user that is subscribed to a room, and sets the value to false. The value being true or false just refers to whether or not the user has read the chat. This is to be used for notifications.
Edit: My question is not a duplicate of this because the MongoDB set command works differently from simply changing the value of an object's property. To add onto that, MongoDB can't even use the notation of object[property], because the docs say the only way to access embedded fields is through dot notation.
Actually those links that #BlakesSeven provided will solve your problem. It should be something like this,
var addedString = "profile.chatInfo.subscribedRooms."+findChatroom._id;
var $set = {};
$set[addedString] = false;
users.update({$where:function() {
return this.profile.chatInfo.subscribedRooms.hasOwnProperty(findChatroom._id);
}}, { $set: $set }, { multi:true })
I want to make a publication with several additional fields, but I don't want to either use Collection.aggregate and lose my publication updates when the collection change (so I can't just use self.added in it either).
I plan to use Cursor.observeChanges in order to achieve that. I have two major constraints:
I don't want to publish all the documents fields
I want to use some of the unpublished fields to create new ones. For example, I have a field item where I store an array of item _id. I don't want to publish it, but I want to publish a item_count field with the length of my field array
Here comes the approach:
I plan to chain find queries. I never did that so I wonder if it possible. The general (simplified) query structure would be like this: http://jsfiddle.net/Billybobbonnet/1cgrqouj/ (I cant get the code properly displayed here)
Based on the count example in Meteor documentation, I store my query in a variable handle in order to stop the changes notification if a client unsubscribes:
self.onStop(function () {
handle.stop();
});
I add a flag initializing = true; before my query and I set it to true just before calling self.ready();. I use this flag to change my itemCount variable only if it is the publication is initialized. So basically, I change my switch like that:
switch (field) {
case "item"
if (!initializing)
itemCount = raw_document.item.length;
break;
default:
}
I wanted to check that this approach is good and possible before committing into big changes in my code. Can someone confirm me if this is the right way to go?
It's relatively easy to keep fields private even if they are part of the database query. The last argument to self.added is the object being passed to the client, so you can strip/modify/delete fields you are sending to the client.
Here's a modified version of your fiddle. This should do what you are asking for. (To be honest I'm not sure why you had anything chained after the observeChanges function in your fiddle, so maybe I'm misunderstanding you, but looking at the rest of your question this should be it. Sorry if I got it wrong.)
var self = this;
// Modify the document we are sending to the client.
function filter(doc) {
var length = doc.item.length;
// White list the fields you want to publish.
var docToPublish = _.pick(doc, [
'someOtherField'
]);
// Add your custom fields.
docToPublish.itemLength = length;
return docToPublish;
}
var handle = myCollection.find({}, {fields: {item:1, someOtherField:1}})
// Use observe since it gives us the the old and new document when something is changing.
// If this becomes a performance issue then consider using observeChanges,
// but its usually a lot simpler to use observe in cases like this.
.observe({
added: function(doc) {
self.added("myCollection", doc._id, filter(doc));
},
changed: function(newDocument, oldDocument)
// When the item count is changing, send update to client.
if (newDocument.item.length !== oldDocument.item.length)
self.changed("myCollection", newDocument._id, filter(newDocument));
},
removed: function(doc) {
self.removed("myCollection", doc._id);
});
self.ready();
self.onStop(function () {
handle.stop();
});
To solve your first problem, you need to tell MongoDB what fields it should return in the cursor. Leave out the fields you don't want:
MyCollection.find({}, {fields: {'a_field':1}});
Solving your second problem is also pretty easy, I would suggest using the collection helpers packages. You could accomplish this easily, like so:
// Add calculated fields to MyCollection.
MyCollection.helpers({
item_count: function() {
return this.items.length;
}
});
This will be run before an object is added to a cursor, and will create properties on the returned objects that are calculated dynamically, not stored in MongoDB.
I have a collection which have a document like this:
collection 1
{
_id: ObjectID(),
name: foo
}
I would get ObjectID of the above collection and copy into a document of another collection in order to reference correctly. Should I do simply:
db.collection1.find({name:"foo"},{_id:1})
EDIT
A call to find will return a cursor. Cursors works like an iterator in other languages. You can either attempt to find the first element in the cursor using the next() function and then get it's _id property or simplify your statement using findOne:
var x = db.collection1.findOne({name:"foo"}, {_id:1});
var id = x._id;
This is making an assumption that you are getting a document back from that query. You'll probably want to add a null check on x before grabbing the _id property.
In mongo I have a collections with records. These record are very complex. Now I would like to duplicate one of them.
I can easily select the one
mongo> var row = db.barfoo.find({"name":"bar"});
Now I actually don't know what to do. I don't know what is in row because I cannot find a way to print its content. How can I change specific properties and finally insert this modified row again
mongo> db.barfoo.insert(row);
thnx
You must change value _id - generate new:
var row = db.barfoo.findOne({"name":"bar"});
row._id = ObjectId();
db.barfoo.insert(row);
Good Luck!
I am going to assume that you're working directly inside the mongo shell.
Once you have your document (not a row :P ), you'd modify the properties in the same way you would a normal JavaScript object:
var doc = db.barfoo.findOne( { "name": "bar" } );
doc.name = "Mr Bar";
Note that the find() command returns a cursor, so if you're looking to extract a single document, you should use the findOne() function. This function returns a single document.
If you are interested in duplicating numerous documents, you can use the find() function and iterate over the cursor to retrieve each document:
db.barfoo.find( { "name": "bar" } ).forEach( function( doc ){
doc.name = "Mr Bar";
}
After you change the relevant properties, you can use the insert/save methods to persist the data back to mongo. Don't forget to change/delete the _id attribute so that you'll actually create a new document.
As a side note, in order to view the contents of an object in the mongo shell, you can use the print() function. If you want a more visually appealing output, you could use printjson().
I made a simple db with a few users in it with mongodb and nodejs. Next im looping through the list and display the users in the list's names etc with sys.puts().
No I am adding the users to an Array() like this:
db.open(function(err, db) {
db.collection('users', function(err, collection) {
collection.find({}, {'sort':[['name', 1]]}, function(err, cursor) {
cursor.each(function(err, user) {
if(user != null) {
users[user._id] = { 'name':user.name, 'email': user.email };
sys.puts(">> Adding user to list... "+ user.name);
}
});
db.close();
});
});
});
Is this how I add the users to the array? Because the users.lenght = 0. Im a bit lost now
What you are doing is setting properties on the array object, that might be a bit confusing.
[] is both used for indexes and keys, that means in case of your array, users[0] will return the first element in the array, but users['blaid12'] will get/set the property blaid12' on the array object, that's like doingusers.blaid12`.
So in the end your array becomes more like a hashmap. The length property does not count the properties of the object, it counts the elements in the array.
You have a couple of ways of solving the issue:
Use an object {} and use the user ids as keys on that object, you'll have to keep track of the user count via another variable.
Use the array as an array by using users.push({'name':...}) to append elements to the array, if you need the userid too, then just add it to the object you push into the array.
Go with a mixed approach, use an array to push the values, and then an object to map the ids to the array indexes.