Mongoose - How to update all objects within an array in MongoDB?

Question

I am creating an app where I want to toggle the default address of a person.
My User Schema contains a field which is an array of delivery addresses which are objects.
One of the fields is isDefault , which is the defaultAddress field I want to toggle from true to false and vice versa.
Specifically, if the user changes their default address, I want to set the rest of the addresses to false and update the one he/she chose to be true

User Schema

const UserSchema = Schema({
 email: {
    type: String,
    required: true,
  },
 deliveryAddresses: [deliverySchema]

Delivery Address Schema

{
      id: {
        type: Schema.Types.ObjectId,
        required: true
      },
      isDefault: {
        type: Boolean,
        required: true,
        default: false,
      },
      name: {
        type: String,
      },
      email: {
        type: String,
      },
      phone: {
        type: String,
      },
     
    }

To do that, what I have done so far is:
Getting the email of the user.
Getting the id of the delivery address from the user that will be toggled to true.

exports.setDefault = (req, res, next) => {
  const email = req.body.email;
  const id = req.body.id;

  User.findOne({ email: email })
    .then((user) => {
      let addresses = [...user.deliveryAddresses];

      addresses.forEach((address) => {
        address.isDefault = false;
      });
    
      const index = addresses.findIndex((address)=> {
          return address.id.toString() === id.toString();
      });

      addresses[index].isDefault = true;
  
      user.deliveryAddresses = addresses;
      return user.save();  
    })
    .then((doc) => {
      res.status(200).json({
        user: doc,
        statusCode: "200",
        msg: "Address updated successfully",
      });
    })

    .catch((err) => {
      res.status(500).json({
        statusCode: 500,
        error: err,
        msg: "Something went wrong",
      });
    });
};

However, after doing all this, on testing my api on postman, it seems to work, no errors. But on checking the database, nothing has changed.
I am at loss as to what I'm doing wrong.

Answer 1

Mongoose is weird. You need to mark the deliveryAddresses sub-object as modified, otherwise its changes won't be saved.

user.markModified('deliveryAddresses');
user.save();

Answer 2

From Mongoose FAQs

"Mongoose doesn't create getters/setters for array indexes; without them mongoose never gets notified of the change and so doesn't know to persist the new value. There are two workarounds: MongooseArray#set or Document#markModified()."

Can you try sth like

user.markModified('deliveryAddresses');
user.save();

More on https://mongoosejs.com/docs/faq.html