First off, sorry for being a complete javascript noob, I am more of a PHP guy and am just testing out the meteor framework.
I am trying to loop through a collection of objects and trying to add a property from another collections as so :
Template.host.hosts = function() {
var hosts = Hosts.find();
hosts.forEach(function(host) {
host.lastPing = Pings.findOne({id: host.id}, {sort: {timestamp : -1}});
// This works fine
// console.log(host.lastPing.id);
});
for (host in hosts) {
// This results in "TypeError: Cannot read property 'id' of undefined"
console.log(host.lastPing.id);
}
return hosts;
};
I don't understand why the second console.log is not working.
I have tried searching but I don't know if the problem is specific to the way meteor handles collections or the way I should be adding properties to a javascript object or someting completely unrelated (scope etc...)
I have simplified my problem to try to understand what is happening, my real problem is obviously looping in a template as per :
{{#each hosts}}
{{this.lastPing.id}}
{{/each}}
Thanks
Three things:
MongoDB and Meteor ids are stored in _id rather than id.
In the context of your forEach method, host iterates through the query set returned by Hosts.find(), but it doesn't actually give you access to the documents themselves. Essentially, it's a copy of the information in the MongoDB rather than the document in the database.
The correct (and only) way to update the actual document is by using the Collection.update method:
Hosts.update({_id: host._id}, {$set: {lastPing: Pings.findOne({id: host.id}, {sort: {timestamp : -1}}) }});
(note that you can only update by _id on the client which is why that's what I've used here, whereas you can supply any query on the server.)
The hosts object is a cursor rather than an array. This means that when you use for host in hosts, you're actually iterating through the properties of the cursor object (which are inherited from the prototype) rather than an array of hosts, and none of them has an id property. One way to make this work is to fetch the query set and put it into hosts like this:
var hosts = Hosts.find().fetch();
Alternatively, you can stick with the cursor and use forEach again, although you'll either have to rewind it with hosts.rewind(), or repeat the line above to reset it to the start of the query set.
Hope that's helpful.
Related
I was wondering how I can query documents from a firestore collection from an array of ID's? I only want the documents in the collection that are in the array of ID's. I looked at another answer and think my approach is correct, however, I am getting an error.
(node:15105) UnhandledPromiseRejectionWarning: TypeError: Cannot read property 'data' of undefined
> at /Users/username/SideProjects/projectname/functions/index.js:40:38
> at processTicksAndRejections (internal/process/task_queues.js:95:5)
The error happens because the function is not finding any documents in the collection from that array of ID's. However, I double-checked the database and know that there are documents in the collection with ID's from the array.
const admin = require('firebase-admin')
....
let feedItems = db.collection(feedItemsCollection)
feedItemsList = feedItems.where(admin.firestore.FieldPath.documentId(), 'in', ['HPOorsSnbHpTYwwXxfWw']).get().then(snapshot2 => {
console.log(admin.firestore.FieldPath.documentId())
console.log("In feed Items")
//console.log(feedItemIds)
console.log(snapshot2[0])
//error happens on this line because snapshot2[0] returns undefined
console.log(snapshot2[0].data())
})
Snapshot2[0] returns undefined which I'm assuming means that no data was returned. I think I'm not properly calling documentId(), but don't know the fix.
There "maybe" two problems with your code. Follow both points to make sure things are working
Data inside snapshot2 maybe empty
You'll first have to fix your code to test this theory. You're not accessing data from snapshot2 correctly. To do it right, one way is this:
// `snapshot2` will have a `docs` property that you can leverage
const snapshot2Data = snapshot2.docs.map((doc) => doc.data());
.documentId() may not be doing what it's supposed to (as you said)
To test this theory, check if snapshot2Data is empty. Run :
console.log(snapshot2Data); // what do you get ?
If no, it's not empty and you got data back, then you're all set. Nothing more to do
If yes, it is empty, then run :
console.log(admin.firestore.FieldPath.documentId()); // what do you get ?
Did you get back a string? If no, then we have another problem. You'll need to take a closer look at your firebase-admin setup, as well.
Problem
In a social media app I am making with react native and firebase, I am trying to grab the number of comments a post has using the snapshot function of a variable I have saved on my servers, then I am going to add one to this variable when a user adds a new comment. My code to do so is right here:
firebase.database().ref('posts').child(this.state.passKey).update({
comments: firebase.database().ref('posts/'+this.state.passKey).child('comments').snapshot.val() + 1
})
When I actually run this code, I get an error saying:
Reference.child failed: First argument was an invalid path = "undefined".
Paths must be non-empty strings and can't contain ".","#","$","[", or "["
At first I thought this might be that the "this.state.passKey" wasn't actually passing the key, but putting in a key I copied from the server didn't fix the problem.
My Server
-
To get the comments of particular post you should do like this
let postId='someId'
postRef=`/posts/${postId}`
firebase.database().ref(postRef).once("value", dataSnapshot => {
comment=dataSnapshot.val().comments
});
It looks like you're expecting this bit of code to query the database:
firebase.database().ref('posts/'+this.state.passKey).child('comments').snapshot.val() + 1
Unfortunately, it doesn't work that way. There's no snapshot property on a database Reference object returned by child() or ref().
Instead, you'll need to query the database at that reference, then when you're called back with its value, you can apply it elsewhere.
var ref = firebase.database().ref('posts/'+this.state.passKey+'/comments')
ref.once('value', function(snapshot) {
// use the snapshot here
})
I'm working on Meteor, trying to find some values from Mongodb collection.
here is the code:
var sameLogins = Users.findOne({login: 'a'});
console.log(sameLogins);
But it's returning and "undefined".
But record exists in collection:
So, can anybody tell what I'm missing?
Also, in mongo console - everything is working fine:
I was looking in Publish/Subsribe stuff, but i'm using autopublish module yet.
Thank you!
I will leave the answer for this issue for new users having the same problem.
If you're using autopublish package then you should be aware that it's publishing the result of .find() for every collection.
But, Meteor.users.find(), be default, will return only _id and profile fields, so documents in your Meteor.users client collection will have these two fields only.
The most easy workaround for this would be to create your own publication (allUsers, for example) and in it to return those fields you need:
Server:
Meteor.publish('allUsers', () => {
// check for Meteor.userId() is omitted, put it here, if needed
return Meteor.users.find({}, { fields: { ... } });
});
Don't forget to subscribe to it:
Client:
Meteor.subscribe('allUsers');
Update for Meteor:
Right now you are storing a cursor in your variable sameLogins. In order to retrieve the results you want, you must actually execute this query by either calling fetch(). What is returned from findOne without fetch is essentially an object that you could use to iterate over and find mongoDB documents - (called a collection cursor). The cursor is not your result itself.
Calling fetch would like something like:
Users.findOne({login: 'a'}).fetch()
I am newly using node.js. I am reading the code of one app. The code below is to initialize the db, to load some question into the survey system I can't understand what's remove() and save() means here. Because I can't find any explanation about these two method. It seems mongoose isn't used after being connected. Could any one explain the usage of these methods?
Well, this is my understanding of this code, not sure to be correct. My TA tell me it should be run before server.js.
/**
* This is a utility script for dropping the questions table, and then
* re-populating it with new questions.
*/
// connect to the database
var mongoose = require('mongoose');
var configDB = require('./config/database.js');
mongoose.connect(configDB.url);
// load the schema for entries in the 'questions' table
var Question = require('./app/models/questions');
// here are the questions we'll load into the database. Field names don't
// quite match with the schema, but we'll be OK.
var questionlist = [
/*some question*/
];
// drop all data, and if the drop succeeds, run the insertion callback
Question.remove({}, function(err) {
// count successful inserts, and exit the process once the last insertion
// finishes (or any insertion fails)
var received = 0;
for (var i = 0; i < questionlist.length; ++i) {
var q = new Question();
/*some detail about defining q neglected*/
q.save(function(err, q) {
if (err) {
console.error(err);
process.exit();
}
received++;
if (received == questionlist.length)
process.exit();
});
}
});
To add some additional detail, mongoose is all based on using schemas and working with those to manipulate your data. In a mongodb database, you have collections, and each collection holds different kinds of data. When you're using mongoose, what's happening behind the scenes is every different Schema you work with maps to a mongodb collection. So when you're working with Question Schema in mongoose land, there's really some Question collection behind the scenes in the actual db that your working with. You might also have a Users Schema, which would act as an abstraction for some Users collection in the db, or maybe you could have a Products Schema, which again would map to some collection of products behind the scenes in the actual db.
As mentioned previously, when calling remove({}, callback) on the Questions Schema, you're telling mongoose to go find the Questions collection in the db and remove all entries, or documents as they're called in mongodb, that match a certain criteria. You specify that criteria in the object literal that is passed in as the first argument. So if the Questions Schema has some boolean field called correct and you wanted to delete all of the incorrect questions, you could say Question.remove({ correct: false }, callback). Also as mentioned previously, when passing an empty object to remove, your telling mongoose to remove ALL documents in the Schema, or collection rather. If you're not familiar with callback functions, pretty much the callback function says, "hey after you finish this async operation, go ahead and do this."
The save() function that is used here is a little different than how save() is used in the official mongodb driver, which is one reason why I don't prefer mongoose. But to explain, pretty much all save is doing here is you're creating this new question, referred to by the q variable, and when you call save() on that question object, you're telling mongoose to take that object and insert it as a new document into your Questions collection behind the scenes. So save here just means insert into the db. If you were using the official mongo driver, it would be db.getCollection('collectionName').insert({/* Object representing new document to insert */}).
And yes your TA is correct. This code will need to run before your server.js file. Whatever your server code does, I assume it's going to connect to your database.
I would encourage you to look at the mongoose API documentation. Long term though, the official mongodb driver might be your best bet.
Mongoose basically maps your MongoDB queries to JavaScript objects using schema.
remove() receives a selector, and callback function. Empty selector means, that all Questions will be affected.
After that a new Question object is created. I guess that you omitted some data being set on it. After that it's being saved back into MongoDB.
You can read more about that in the official documentation:
http://mongoosejs.com/docs/api.html#types-subdocument-js
remove query is use for removing all documents from collection and save is use for creating new document.
As per your code it seems like every time the script run it removes all the record from Question collection and then save new records for question from question list.
I'm making my first application using DocumentDB. I'm developing an API for it in Node.js. As others have noted, the DocumentDB APIs are very confusing and appear to require convoluted code to achieve simple things.
My API will allow me to access data in the database with a URL of the form http://<host>/data/<databaseName>/<collectionID>/<documentId>/<pathToData>. If <pathToData> is empty, then I will get the whole document as a JSON object.
I want a function with the signature GetDocument(databaseName,collectionID,documentId,callback), where callback is a function that takes the particular document as a JavaScript object. What implementation of GetFunction achieves my goal?
The DoQmentDB library makes for a trivial solution.
// dbClient: require('documentdb').DocumentClient; new DocumentClient(host,options);
// callback: function(document)
function getDocument(dbClient,databaseId,collectionId,documentId,callback) {
var DoQmentDB = require('doqmentdb');
var db = new DoQmentDB(dbClient,databaseId);
var collection = db.use(collectionId);
collection.findById(documentId).then(callback);
}
You first need your method to initialize a documentclient object with the database and collection parameters, which you do with the readorcreatedatabase and readorcreatecollection methods, as showcased in the documentation. Once you have that object initialized, you can query specific objects by document id or by a custom query string.
Ideally, you should cache those database and collection objects upon first request, so that you don't hit the db asking for the same information upon every single request you issue