Mongoose Model ObjectId References Not Working

Question

I'm working with Mongoose models and references. I've been using the code from mongoose's website where it talks about the populate method and references. I am trying to have it save the respective "referenced" ids in both models. It is only saving the reference ids in the story model. Here is the code:

Update: Added schemas at the top to help:

    var personSchema = Schema({
      _id: Schema.Types.ObjectId,
      name: String,
      age: Number,
      stories: [{ type: Schema.Types.ObjectId, ref: 'Story' }]
    });

    var storySchema = Schema({
      author: { type: Schema.Types.ObjectId, ref: 'Person' },
      title: String,
      fans: [{ type: Schema.Types.ObjectId, ref: 'Person' }]
    });

    var Story = mongoose.model('Story', storySchema);
    var Person = mongoose.model('Person', personSchema);

(end of schemas)

var author = new Person({
  _id: new mongoose.Types.ObjectId(),
  name: 'Ian Fleming',
  age: 50
});

author.save(function (err) {
  if (err) return handleError(err);

  var story1 = new Story({
    title: 'Casino Royale',
    author: author._id    // assign the _id from the person
  });

  story1.save(function (err) {
    if (err) return handleError(err);
    // thats it!
  });
});

When you run this code, it generates this in mongo:

  db.people.find()
  { "_id" : ObjectId("5be0a37f1dd61a343115e2c8"), "stories" : [ ], "name" : "Ian Fleming", "age" : 50, "__v" : 0 }
  db.stories.find()
  { "_id" : ObjectId("5be0a37f1dd61a343115e2c9"), "title" : "Casino Royale", "author" : ObjectId("5be0a37f1dd61a343115e2c8"), "__v" : 0 }

It appears to not be storing any ids in the people collection within "stories." Wouldn't you want to save the stories ids in the people collection as well?

I tried to modify the code to make it work with (moved the author save function, until after the story id is set):

 var author = new Person({
  _id: new mongoose.Types.ObjectId(),
  name: 'Ian Fleming',
  age: 50
 });

  var story1 = new Story({
    _id: new mongoose.Types.ObjectId(),
    title: 'Casino Royale',
    author: author._id    // assign the _id from the person
  });

  author.stories = story1._id;

  author.save(function (err) {
  if (err) return handleError(err);

  story1.save(function (err) {
    if (err) return handleError(err);
    // thats it!
  });

This gives me an author undefined.

Jim B. · Answer 1 · 2018-11-06T01:27:24.200

0

Mongo wouldn't automatically add to the Person "stories" field just because you added a Story object.

You don't really need to store the story ids in Person objects anyway, as you can always get a list of stories by an author with

db.stories.find({author: <id>})

Storing in both places would create redundant information and you'd have to pick one to be the truth in the case of a mismatch. Better to not duplicate, methinks.

UPDATE:

References appear to help you populate referenced fields in queries automatically. According to this post you can retrieve an author and their stories like this:

db.persons.find({_id: <id>}).populate('stories')

Haven't personally used this but it looks pretty handy.

Mongoose docs for populate: https://mongoosejs.com/docs/populate.html

edited Nov 06 '18 at 01:27

answered Nov 05 '18 at 22:25

Jim B.

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That makes sense... they do include a "stories" property in the Person schema. I wonder if that is just for reference (no pun intended) and not actually needed, in this particular case. I'll add their schema to the question. – seoandcode Nov 05 '18 at 22:37
Perhaps what "they" are doing is explained here: https://stackoverflow.com/questions/18001478/referencing-another-schema-in-mongoose – Jim B. Nov 06 '18 at 01:23

Mongoose Model ObjectId References Not Working

1 Answers1