Mongoose update/insert value into array of objects

Question

So I have this data stored in a mongodb database:

{
    _id: 'string',
    email: 'string',
    purchases: [
        { name: 'item 1', cost: 45, quantity: 3 },
        { name: 'item 2', cost: 62, quantity: 2 },
        { name: 'item 3', cost: 14, quantity: 7 },
    ]
}

What I am trying to do is search for the user id (._id) and the item in the purchases array by the item name, so for item 1:

{ _id: req.body._id, purchases: { $elemMatch: { name: 'Item 1' }}}

This query works fine. However the behavior I need is if the item exists, modify the quantity value to reset to one. If the item doesn't exist, i.e. its a new item, I want to insert a new item object.

I thought that .findOneAndReplace would work for this, so my code is:

    User.findOneAndReplace(
        { _id: req.body._id, purchases: { $elemMatch: { name: 'Item 1' }}},
        { $push: { purchases: { name: req.body.name, cost: req.body.cost, quantity: 1 }}},
        {
            upsert: true
        }
    ).then((result) => {
        res.status(200).json({
            message: 'Added score :D'
        })
    }).catch((error) => {
        res.status(400).json({
            message: 'Failed to add score...' + error
        })
    })

but this obviously doesn't work. I can insert a new value into the purchases array but I cant update a current result if it exists.

Someone Special · Accepted Answer · 2022-02-07 05:14:12Z

1

What you are doing is actually not a good way to handle documents.

A better way to handle your problem is to create a different model for purchases.

const purchases = mongoose.Schema({
      name: String,
      cost: Number,
      quantity: Number,
      user: { type: mongoose.Schema.Types.ObjectId, ref: 'User' }
})

Instead of adding purchases to the User model, you will create a new entry under purchases.

To update purchases, you can just update each purchase document directly.

If you want to retrieve all purchases for a user, you can simply

 Purchases.find({ user: user._id })

To see if item exist.

 Purchases.find({ user: user._id, name: 'Item 1'});

You can also find the purchases through the user model using $lookup.

 Users.aggregate([
       {
          $match: { _id: user._id }
       },
       {
          $lookup: {
              from: 'purchases',
              localField: "_id",
              foreignField: "user",
              as: "purchases"
          }
       },
       {
          $project: {
               ....fields you want to return ....
          }
       }
 ])

In the long run you will find this model of database more efficient and easier to up keep, and there's more pros than cons separating the documents into different collections.

answered Feb 7, 2022 at 5:14

Someone Special

13.7k8 gold badges54 silver badges80 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Bogomip Over a year ago

Thanks - I guess I was trying to avoid creating multiple reads where possible but this is by far a nicer solution. Much appreciated!

Collectives™ on Stack Overflow

Mongoose update/insert value into array of objects

1 Answer 1

1 Comment

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Linked

Related