I am very new to mongodb and have a basic question that I am having trouble with. How do I get the ID field of a document that has already been created? I need the ID so i can update/add a new field to the document.
//newProfile is an object, one string it holds is called school
if(Schools.find({name: newProfile.school}).fetch().length != 1){
var school = {
name: newProfile.school
}
Meteor.call('newSchool', school);
//Method 1 (doesn't work)
var schoolDoc = Schools.findOne({name: newProfile.school});
Schools.update({_id: schoolDoc._id}, {$set: {enrolledStudents: Meteor.user()}});
//Method 2?
//Schools.update(_id: <what goes here?>, {$push: {enrolledStudents: Meteor.user()}});
}
else {
//Schools.update... <add users to an existing school>
}
I create a new school document if the listed school does not already exist. Schools need to hold an array/list of students (this is where i am having trouble). How do I add students to a NEW field (called enrolledStudents)?
Thanks!
I'm having some trouble understanding exactly what you're trying to do. Here's my analysis and understanding so far with a couple pointers thrown in:
if(Schools.find({name: newProfile.school}).fetch().length != 1){
this would be more efficient
if(Schools.find({name: new Profile.school}).count() != 1) {
Meteor.call('newSchool', school);
Not sure what you're doing here, unless you this will run asynchronously, meaning by the time the rest of this block of code has executed, chances are this Meteor.call() function has not completed on the server side.
//Method 1 (doesn't work)
var schoolDoc = Schools.findOne({name: newProfile.school});
Schools.update({_id: schoolDoc._id}, {$set: {enrolledStudents: Meteor.user()}});
Judging by the if statement at the top of your code, there is more than one school with this name in the database. So I'm unsure if the schoolDoc variable is the record you're after.
I believe you are having trouble because of the asynchronous nature of Meteor.call on the client.
Try doing something like this:
// include on both server and client
Meteor.methods({
newSchool: function (school) {
var newSchoolId,
currentUser = Meteor.user();
if (!currentUser) throw new Meteor.Error(403, 'Access denied');
// add some check here using the Meteor check/match function to ensure 'school'
// contains proper data
try {
school.enrolledStudents = [currentUser._id];
newSchoolId = Schools.insert(school);
return newSchoolId;
} catch (ex) {
// handle appropriately
}
}
});
// on client
var schoolExists = false;
if (Schools.findOne({name: newProfile.school})) {
schoolExists = true;
}
if (schoolExists) {
var school = {
name: newProfile.school
};
Meteor.call('newSchool', school, function (err, result) {
if (err) {
alert('An error occurred...');
} else {
// result is now the _id of the newly inserted record
}
})
} else {
}
Including the method on both the client and the server allows Meteor to do latency compensation and 'simulate' the insert immediately on the client without waiting for the server round-trip. But you could also just keep the method on the server-side.
You should do the enrolledStudents part on the server to prevent malicious users from messing with your data. Also, you probably don't want to actually be storing the entire user object in the enrolledStudents array, just the user _id.
For what you're trying to do, there is no need to get the _id. When you use update, just switch out the {_id: schoolDoc._id} with your query. Looks like using {name: newProfile.school} will work, assuming that the rest of your code does what you want it to do.
While that would work with the normal Mongo driver, I see that Meteor does not allow your update query to be anything but _id: Meteor throws throwIfSelectorIsNotId exception
First, make sure that you're pulling the right document, and you can try something like this:
var school_id = Schools.findOne({name: newProfile.school})._id;
Schools.update({_id: school_id}, { $push: { enrolledStudents: Meteor.user()}});
If that doesn't work, you'll have to do a little debugging to see what in particular about it isn't working.
Related
I have to connect to the external database and get access to its collections. It works fine, when I use it, but the problem is when I need collection hooks, e.g. Collection.after.insert(function(userId, doc)). The hook is not being fired. I have following code:
// TestCollection.js
let database = new MongoInternals.RemoteCollectionDriver("mongodb://127.0.0.1:3001/meteor",
{
oplogUrl: 'mongodb://127.0.0.1:3001/local'
});
let TestCollection = new Mongo.Collection("testCollection", { _driver: database });
module.exports.TestCollection = TestCollection;
console.log(TestCollection.findOne({name: 'testItem'})); // writes out the item correctly
// FileUsingCollection.js
import { TestCollection } from '../collections/TestCollection.js';
console.log(TestCollection.findOne({name: 'testItem'})); // writes out the item correctly second time
TestCollection.after.update(function (userId, doc) {
console.log('after update');
}); // this is NOT being fired when I change the content of remote collection (in external app, which database I am connected)
How to make this work?
EDIT:
I have read many hours about it and I think it might be connected with things like:
- oplog
- replicaSet
But I am newbie to Meteor and can’t find out what are those things about. I have set MONGO_OPLOG_URL and I added oplog parameter to database driver as I read here: https://medium.com/#lionkeng/2-ways-to-share-data-between-2-different-meteor-apps-7b27f18b5de9
but nothing changed. And I don’t know how to use this replicaSet, how to add it to the url. Anybody can help?
You can also try something like below code,
var observer = YourCollections.find({}).observeChanges({
added: function (id, fields) {
}
});
You can also have 'addedBefore(id, fields, before)', 'changed(id, fields)', 'movedBefore(id, before)', 'removed(id)'
For more features goto link.
I have two models defined like this:
var OrganizationSchema = new mongoose.Schema({
users: [mongoose.Schema.Types.ObjectId]
});
and
var UserSchema = new mongoose.Schema({
organizations: [mongoose.Schema.types.ObjectId]
});
When a user want to join an organization I need to update both the organization collection and the user collection. I want to know what is the best way to achieve this ? Is it worth considering the case when one update request fail ? I'm currently doing something like this (where organization is a collection instance of the model Organization):
User.findByIdAndUpdate(req.userSession.userId, { $push: { organizations: organization.id } }, function (err){
if (err)
{
// server error
console.log(err);
}
else
{
organization.users.push(req.userSession.userId);
organization.save(function (err){
if (err)
{
// server error we need to cancel
User.findByIdAndUpdate(req.userSession.userId, { $pull: { organizations: organization.id } }, function (err){
if (err)
{
// we got a problem one collection updated and not the other one !!
console.log(err);
}
});
}
else
{
// success
}
});
}
});
The problem is: if my second update method fail I will end up with one collection updated and not the other ? Is there a way to make sure they are both updated ?
Well firstly, I would stay clear of that design. I would either reference or embed user in organisations and the other way around, not both of them at same time, so I wouldn't have problems like this(which happens every-time you duplicate data).
MongoDB doesn't have support for simultaneous updates, or transactions. So you are left to manage this in your code.
So yes, if the second update fails, then as you wrote your code you have to rollback, and if the rollback fails, you have to retry till it succeeds(though with exponential backoff probably). Keep in mind that might intefer with other requests(another user tries to save the same thing simultaneously). To handle that you have to give a unique to each entry in the array.
I have a problem I can't find an answer to in Loopback's docs.
Say I have a model Company and a modelEmployee. There is an 1Xn relation between the Company and its Employees. When /api/Employees is called, server returns all the employees.
I only want to return the list of employees who are in the same company with the user requesting the list.
For this, I created a remote hook
Employee.beforeRemote('find', function(context, modelInstance, next) {
var reject = function() {
process.nextTick(function() {
next(null, false);
});
};
// do not allow anonymous users
var userId = context.req.accessToken.userId;
if (!userId) {
return reject();
}
//I get the details of the user who sent the request
//to learn which company does he belong to
Employee.findById(userId, function(err, user) {
if(!context.req.query.filter) context.req.query.filter={};
context.req.query.filter.where = {brandId:user.companyId};
console.log(context.req.query);
next();
});
});
I thought this should work every time, but appearantly it only works when find already has some query filters like include - although the console.log prints a correct context.req.query object.
What am I missing? Any help would be greatly appreciated!
context.args.filter seems to work for this purpose.
As a side note, instead of replacing where, you might want to merge it with something provided by client. For implementation idea you can refer to: https://github.com/strongloop/loopback-datasource-juggler/blob/master/lib/utils.js#L56-L122
Suppose I have a document for example: var doc = Model.findOne({name:"name"});
Now if the document gets edited trough another connection the the database, doc doesn't hold the right information. I do need it, so I have to "refresh" or "redownload" it from the database. Is there any way to do this with only the object "doc"?
Assuming doc contains the document instance to refresh, you can do this to generically refresh it:
doc.model(doc.constructor.modelName).findOne({_id: doc._id},
function(err, newDoc) {
if (!err) {
doc = newDoc;
}
}
);
However, it's better to not persist/cache Mongoose document instances beyond your immediate need for them. Cache the immutable _id of docs you need to quickly access, not the docs themselves.
Sorry I know this is old but I have a better solution in case anyone else is still looking around.
What you can do in this situation of concurrent access to the same document is perform a normal save.
Mongoose uses the __v property of an object to make sure old instances don't overwrite the newest ones.
So if you have 2 instances of doc.__v = 0, and A saves first, the db now has doc.__v = 1. So that when B saves, it'll error and because B.__v = 0, not 1. So what you can do is then catch the error (it should be a specific mongoose error) and handle it by refreshing the object, (which should bump it up to __v = 1) then either SAVE it or not SAVE it depending on what you want to do.
so in code
doc.save(function (err, _doc) {
if (err) {
if (err.some_error_property_telling_you_version_was_wrong) {
// Do your business here
// Refresh your object
// Model.findById(doc._id, function (err, _refreshed_doc) {});
// doc = _refreshed_doc;
// doc.set('property', value); set the value again
// Then re-save? or maybe make this a recursive function,
// so it can keep trying to save the object?
} else {
// Handle it like a normal error
}
}
});
If it's defined with let you can just do
await thing.update(stuff);
thing = await Thing.findById(thing._id);
or if it was with const then do it immutably:
await thing.update(stuff);
const updatedThing = await Thing.findById(thing._id);
I have this code
App.Model('users').find(function (err, users) {
users.forEach(function(user) {
console.log(user.username);
});
});
//make usernames availible here.
This console logs the usernames.
Instead of just logging to the console I want make use of the data.
But How can do this?
Thanks
They will never be available where you want them. This isn't how async/node.js programming works.
Possible:
App.Model('users').find(function (err, users) {
users.forEach(function(user) {
myCallBack(user);
});
});
var myCallBack = function(user) {
//make usernames availible here.
//this will be called with every user object
console.log(user);
}
Other possibilites: EventEmitter, flow controll libraries (e.g. async).
If you have written code in other languages before you need to be open to take a complete new approach how data will be handled.
With node js you don't do:
//make usernames availible here.
You do:
App.Model('users').find(function (err, users) {
//usernames are available here. Pass them somewhere. Notify some subscribers that you have data.
});
//The code here has executed a long time ago