MongoDB populate() to dynamically load/migrate data not working - node.js

Question

I am building an app in which the user adds and deletes objects (Pic) in an array('pics') after registering, but not sure how to dynamically load or populate('pics') to userSchema to automatically render. The user registers on the app with that array originally empty ('pics' = zero), and will create or delete those objects thereafter when logged in.
Following the documentation, I used "await User.find().populate('pics');" to migrate data in index method, but did not work.
Besides, should I include 'pics' key at store method, or userSchema 'pics' should be enough?
const userSchema = new mongoose.Schema({
name: {
type: String,
required: true,
trim: true
},
pics: [
{
type: mongoose.Schema.Types.ObjectId,
ref: "Pic"
}
],
});
const picSchema = new mongoose.Schema({
thumbnail: String,
description: String,
dev: {
type: mongoose.Schema.Types.ObjectId,
ref: 'User'
},
},
);
const User = mongoose.model('User', userSchema);
const Pic = mongoose.model('Pic', picSchema)
async index(req, res, next) {
const users = await User.find().populate('pics');
res.status(200).json(
devs
);
},
async store(req, res) {
try {
const { name } = req.body;
let user = await User.create({
name,
pics
})
// await user.populate('pics').execPopulate();
res.send({ user })
}
} catch (error) {
res.status(400).send(error);
}
},

Answer 1

I worked a time ago with MongoDB and NodeJS. I think that you have a problem with the definitions. Also, you can read the documentation https://mongoosejs.com/docs/populate.html
You need to define the _id for collections (Schema).
const userSchema = new mongoose.Schema({
_id: new mongoose.Types.ObjectId(),
name: {
type: String,
required: true,
trim: true
},
pics: [
{
type: mongoose.Schema.Types.ObjectId,
ref: "Pic"
}
],
});
const picSchema = new mongoose.Schema({
_id: new mongoose.Types.ObjectId(),
thumbnail: String,
description: String,
dev: {
type: mongoose.Schema.Types.ObjectId,
ref: 'User'
},
},
);
So, when you create a new User, the _id is completed (you can generate it or it can be generated automatically) and ignore the field pics. When you create a Pic, you need to read the _id of the User and assigned as 'dev', something like:
let pic = new Pic({
thumbnail: '', description: '',
dev: yourUser._id
});
Using this way to create documents, you can use the populate function.