Meteor / Mongo 'findOne' function returning "undefined"

Question

I'm (obiously) a beginner, first post. I'm creating a flashcards project with Meteor. I have a db called "cardsets" that contains lots of documents that look similar to this:

{ "_id" : "asdfg00724", 
"setTitle" : "Les animaux", 
"vocab" : [ 
[ "the dog", "le chien" ],
[ "the cat", "le chat" ], 
[ "the rabbit", "le lapin" ], 
[ "the horse", "le cheval" ] ] }

What I'm trying to do is to access a single document from the collection and assign each field in the document to a variable of the same name, with the 'vocab' field being brought in as an array.

I have an /imports/api/cardsets.js that contains this:

import { Mongo } from 'meteor/mongo';
export const Cardsets = new Mongo.Collection('cardsets');

The /server/main.js includes this line:

import '../imports/api/cardsets.js';

And the /client/main.js file includes this line:

import { Cardsets } from '/imports/api/cardsets.js';

In the /client/main.js file, I am able to directly 'insert' new documents into the database, so I know the Cardfiles const is accessible in main.js:

Cardsets.insert( {language: "Chinese", course: "CHIN102"});

Works as expected. (This is only for testing). However, NOTHING I have done with the "findOne" has produced any results:

var asdf = Cardsets.findOne( { _id : "asdfg00724"});
console.log("asdf = "+asdf);

Produces "asdf = undefined" in the console.

And if I type "Cardsets.find({}).fetch()" in the browser console, I get an error: "Cardsets is not defined."

I've tried this as well:

Cardsets.findOne({ _id : "asdfg00724"}, function(err, document) {
     console.log(document.name);
     });

But this produces a huge error containing the text "Match error: Failed Match.OneOf, Match.Maybe or Match.Optional validation".

I realize that there's probably a very easy thing I'm missing, but after working on this for many days non-stop, I felt it's time to ask for help.

Do you have meteor:autopublish working? Or how do you expect those documents to be populated to client? — Styx
(1) find() and findOne() do not accept callbacks as parameters, hence your huge error. (2) your variables (including collections) will not be available in the console unless you're at a breakpoint inside a function where those variables are defined, (3) most likely you're trying to access Cardsets before the client has received that data from the server via pub-sub. Once you implement actual publications and subscriptions you'll be able to look at the .ready() state of subscriptions to know when your data is available. — Michel Floyd
Looking at everything you've got, this should work. Can you upload a reproduction to github? — coagmano
Thanks for the comments! I moved the findOne() statement to a later function and everything worked as expected. Apparently @MichelFloyd was right: the data hadn't had time to be loaded. I was also able to get all the keys assigned to variables, so basically my whole problem is solved. Now to figure out how to mark this question as answers/solved... — Will Lehman

Michel Floyd Michel Floyd · Accepted Answer · 2017-10-31T00:23:54

find() and findOne() do not accept callbacks as parameters, hence your huge error.
your variables (including collections) will not be available in the console unless you're at a breakpoint inside a function where those variables are defined,
most likely you're trying to access Cardsets before the client has received that data from the server via pub-sub. Once you implement actual publications and subscriptions you'll be able to look at the .ready() state of subscriptions to know when your data is available.

Meteor / Mongo 'findOne' function returning "undefined"

1 Answers