MongoDB/Mongoose - Adding an object to an array of objects only if a certain field is unique

Question

So I have a nested array of objects in my MongoDB document and I would like to add a new object to the array only if a certain field (in this case, eventId) is unique. My question is very similar to this post, only I cannot seem to get that solution to work in my case.

Here is what the documents (UserModel) look like:

{
  "portal" : {
    "events" : [ 
      {
        "important" : false,
        "completed" : false,
        "_id" : ObjectId("5c0c2a93bb49c91ef8de0b21"),
        "eventId" : "5bec4a7361853025400ee9e9",
        "user_notes" : "My event note"
      },
      ...and so on
    ]
  }
}

And here is my (so far unsuccessful) Mongoose operation:

UserModel.findByIdAndUpdate(
  userId,
  { "portal.events.eventId": { $ne: req.body.eventId } },
  { $addToSet: { "portal.events": req.body } },
  { new: true }
);

Basically I am trying to use '$ne' to check if the field is unique, and then '$addToSet' (or '$push', I believe they are functionally equivalent in this case) to add the new object.

Could anyone point me in the right direction?

Cheers, Gabe

Why dont you use findOneAndUpdate and have the `$ne: req.body.eventId` inside your query? Also, findByIdAndUpdate only takes 3 parameters (if 4, the last one would be a callback), and you are sending 4 parameters — iagowp, Dec 08 '18 at 21:45

Akrion · Accepted Answer · 2018-12-08T22:54:24.393

If you look into the documentation on your method you will see that the parameters passed are not in the proper order.

findByIdAndUpdate(id, update, options, callback)

I would use update instead and have your id and portal.events.eventId": { $ne: req.body.eventId } part of the initial filter followed by $addToSet: { "portal.events": req.body }

Something among these lines:

UserModel.update(
  { 
     "_id": mongoose.Types.ObjectId(userId), 
     "portal.events.eventId": { $ne: req.body.eventId }
  },
  { $addToSet: { "portal.events": req.body } },
  { new: true }
);

score 1 · Answer 2 · answered Dec 08 '18 at 21:45

You need to include your eventId check into condition part of your query. Because you're usig findByIdAndUpdate you can only pass single value matched against _id as a condition. Therefore you have to use findOneAndUpdate to specify custom filtering condition, try:

UserModel.findOneAndUpdate(
    { _id: userId, "portal.events.eventId": { $ne: req.body.eventId } },
    { $addToSet: { "portal.events": req.body } },
    { new: true }
);

MongoDB/Mongoose - Adding an object to an array of objects only if a certain field is unique

2 Answers2