Mongoose (array in array) - how to insert?

Question

Hello, I would like to insert data into "rss" array. How can I do this? That's how I add new categories into users collection:

  user.findOneAndUpdate({
    _id: req.body.ownerId
  },
  { $push: {
    categories: {
      name: req.body.categoryName,
      public: false
    }
  }},
  { safe: true, upsert: true },
  function(err, model) {
    console.log(err);
  });

But how can I add something into Sport/rss? Firstly I need to find an user by id and secondly I need to find a category also by id. How to do that and finally insert into?

my variables: req.body.ownerId - user id req.body.categoryId - category id req.body.url - rss url which I want to insert into categories array

Thanks for you help.

I edited a bit the image to make it more clear. Why u need the code from image? It's just from node console. — elzoy
– elzoy, Commented Jan 17, 2016 at 3:07
Images shouldn't be used unless absolutely necessary. If there's no need for it then it shouldn't be there. — Alexis Tyler
– Alexis Tyler, Commented Jan 17, 2016 at 3:07
In my opinion the image is necessary here. Thanks for your help. — elzoy
– elzoy, Commented Jan 17, 2016 at 3:09
You can copy the code from the image and paste into your question. This way, one can still view the code even if they can't view the images on their system. — gnerkus
– gnerkus, Commented Jan 17, 2016 at 3:45

gnerkus · Accepted Answer · 2016-01-17 03:41:03Z

1

It is not recommended that you maintain an array within an array. It is often better to maintain a separate collection for the categories.

That said, you'll need to execute two queries: one to populate the categories array for the user and the other to populate the rss array in the categories array for the same user.

In the first update query:

// Populate the 'categories' array. Insert the empty 'rss' array.
...
{ $push: 
  categories: {
    name: req.body.categoryName,
    public: false,
    rss: []
  }
}
...

In the second update query:

// Populate the 'rss' array for the same user.
...
{ $push:
  'categories.$.rss': req.body.url
}
...

The second update query will be executed in the callback of the first one.

answered Jan 17, 2016 at 3:41

gnerkus

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4 Comments

P Ackerman Over a year ago

I actually had this same issue the other day. So arrayName.$.arrayName allows you access the nested array for updating (whether $push or $addToSet?)

gnerkus Over a year ago

Yes, it does. The $ indicates you want to update the array without specifying the index.

elzoy Over a year ago

Hello, thank you for your reply. I've inserted "categories" into users collections because every user will have his own categories (that's his own kind of organizer). In situations like that, there is still better to make categories as new collection?

gnerkus Over a year ago

It is better. Once you store the categories in another collection, you'll store the ids of the categories the user owns in the categories array. mongoose provides the populate command to make that easier.

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