Mongoose.populate() returns empty array instead of data

Question

I've looked up other questions including this one however I couldn't find an answer resolves my problem.

I have defined my models in the same way described in official documentation of mongoose by showing references and defining types of models as Schema.Types.ObjectId. Here they are:

story_model.js

var storySchema = new Schema({
    ...
    candidateParts: [{ type: Schema.Types.ObjectId, ref: 'StoryPart'}],
    ...
}, { usePushEach: true});

storyPart_model.js

var storyPartSchema = new Schema({
    ...
    storyId: { type:Schema.Types.ObjectId, ref: 'Story' },
    ...
}, { usePushEach: true});

And, I have built a query like that where ObjectID = require('mongodb').ObjectID; and storyModel is Story passed through storyController.js

Here is how I call populate:

StoryController.prototype.getCandidateParts = function (storyId, callback) {
var me = this;
const id = { '_id': ObjectID(storyId) };
me.storyModel.findOne(id).populate('candidateParts').exec(function(err,story) {
    if (err) return callback(err, new me.ApiResponse({ success: false, extras: { message: me.ApiMessages.DB_ERROR }}));
    if (story) {
        return callback(err, story);
    }else {
        return callback(err, new me.ApiResponse({ success: false, extras : { message: me.ApiMessages.STORY_NOT_EXISTS }}));
    }
});
};

Following is how I check results of my new populated story:

me.getCandidateParts(story._id, (err, populatedStory) => {
        if (err) {
            return;
        }
        if (populatedStory) {
            console.log(populatedStory);

But I get this result instead of story with populated parts:

[ { _id: 5a8bfaab78798703c0760bd1,
__v: 2,
is_updated: 2018-02-20T10:38:32.620Z,
is_created: 2018-02-20T10:38:32.620Z,
candidateParts: []
... } ]

By the way, I'm sure candidateParts include in database something like that:

ObjectId("5a8bfa33cd601903b57329ab")

And yes, I'm also sure that I have defined model references with exactly the same identifiers.

Thanks in advance!

If you remove the .populate('candidateParts') part, does the result logged in console.log(populatedStory) have anything in the candidateParts array? — chridam
– chridam, Commented Feb 20, 2018 at 12:03
@chridam yes, id of part returns like that [ 5a8c2df95eb65602b02e0687 ] — Yusuf Ak
– Yusuf Ak, Commented Feb 20, 2018 at 14:19
And if you query the storyparts collection in mongo shell with that id e.g db.storyparts.findOne({ _id: ObjectId("5a8c2df95eb65602b02e0687") }) do you get any document as a result? — chridam
– chridam, Commented Feb 20, 2018 at 14:23
@chridam I have found I had same ID for StoryPart and Story instances. I should have something wrong during saving new parts. — Yusuf Ak
– Yusuf Ak, Commented Feb 20, 2018 at 14:40

Yusuf Ak · Accepted Answer · 2018-02-20 15:32:22Z

2

I realized that somehow I have same ID for StoryPart and Story instances. That's why it returns nothing.

EDIT:

I have resolved the problem by ensuring and correcting IDs of story and storypart. I do not delete the question since there might be people facing the same problem, so just check your ObjectIDs if they refer to correct instances.

edited Feb 20, 2018 at 15:32

answered Feb 20, 2018 at 14:39

Yusuf Ak

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