更新嵌套数组并在此之前用猫鼬填充

Question

I would like to add a photo into a country in mongoose. But country is an array and photo too. Here is my user schema :

const UserSchema = new mongoose.Schema({
    name: {
        type: String,
        required: true
    },
    firstName: {
        type: String,
        required: true
    },
    email: {
        type: String,
        required: true,
        unique: true
    },
    password: {
        type: String,
        required: true
    },
    birthDate: {
        type: Date,
        required: true
    },
    sex: {
        type: String,
        required: true
    },
    countries: [
        {
            type: mongoose.Schema.Types.ObjectId,
            ref: 'Country',
            photos: [
                {
                    base64: {
                        type: String,
                        required: true       
                    },
                    title: String,
                    description: String
                }
            ]
        }
    ],
    admin: {
        type: Number,
        required: true
    }
});

Here is what I got as data into mongoDB :

The problem is that I only got the id of countries. And I would like to use another field of the document country. Populate works well when I want to get data, but how to populate and then use the fields to update with mongoDB?

Moreover, I don't know how to update data into nested array, I tried :

User.findOneAndUpdate(
    {
        "name": "CHARLAT",
        "countries": "5d2d847b06f2f94118a36518"
    },
    { $push : { "countries.photos" : {
        base64: "bla"
    } }}
)

As you can see, I use a hand written id for country... I could do a find query before on country but can we use populate here?

And I got this in Postman :

Thank you in advance for your help !

Answer 1

If the type is ObjectId , it can't have a photos field, since it's just an _id . It is a reference to another collection.

Updated answer after comments :

The best thing to do IMO is to create a Photo model which would have the file path and the country's _id. The User model would only store a list of Photos [_id].

UserSchema :

{
   .....
   photos : [{
            type: mongoose.Schema.Types.ObjectId,
            ref: 'Photo'
    }],
   .....
}

PhotoSchema :

{
    country : {
            type: mongoose.Schema.Types.ObjectId,
            ref: 'Country'
    },
    path : String
}

Then, query your Users this way, by populating the photos, and inside each photo, populating the countries :

UserModel
        .find(conditions)
        .populate({ 
             path: 'photos',
             model: 'Photo'
             populate: {
                 path: 'country',
                 model: 'Country'
            } 
         })
         .lean() // Faster and lighter for read-only, simply returns an object

So you should get a User object like this :

{
    .....
    name : "John",
    photos : [{
         country : {
              name : "Country 1",
              code : "C1" // or whatever field you have in your Country model
         },
         path: "path/to/photo1.jpg"
    },
    {
         country : {
              name : "Country 2",
              code : "C2"
         },
         path: "path/to/photo2.jpg"
    }]
    .....
}