mongoose populate in array of custom objects - node.js

Question

In the user model, I have an array of custom objects followedPlaylists which contains two attributes ( playlist: the id of the playlist, public: to determine whether it is public or not) as shown below
const userSchema = new mongoose.Schema({
..... other attributes
followedPlaylists: [{
playlist: {
type: mongoose.Schema.ObjectId,
ref: 'Playlist',
unique: true
},
public: Boolean
}]
})
I want to populate on followedPlaylists.playlist so the response would be something like
[{
playlist: * the actual playlist object *,
public: true
}]
I hope my question is clear enough and thanks in advance.

Answer 1

Here I am assuming that your Playlist is working just fine. i.e., it has elements and has been tested independently.
So, given the schema:
Const Playlist = require (./Playlist)//here you have to provide the path to the Playlist model or use mongoose.model (“Playlist”) to bring it in
………….
const userSchema = new mongoose.Schema({
..... other attributes
followedPlaylists: [{
playlist: {
type: mongoose.Schema.ObjectId,
ref: 'Playlist',
unique: true
},
public: Boolean
}]
})
On whatever you want to print it, just make something like:
Const user = mongoose.model (“User”);//or use require, what fits best your applications
……
Console.log(user.find().populate(“Playlist”))//here is the trick, you ask to populate the Playlist
Example
Examples are the best way to grasp a concept. You can play around with this example:
//------------------------------------------------------------------
const mongoose = require("mongoose");
const { model, Schema } = require("mongoose");
var dbURI = "mongodb://localhost/mongoose-sample";
const app = require("express")();
mongoose
.connect(dbURI, { useNewUrlParser: true, useUnifiedTopology: true })
.then(console.log(`connected to ${dbURI}`));
//----------------------------------------------------------------------
const departmentSchema = new Schema({ name: String, location: String });
const Department = model("department", departmentSchema);
const EmployeeSchema = new Schema({
firstName: String,
lastName: String,
department: { type: mongoose.Types.ObjectId, ref: "department" }
});
const Employee = model("employee", EmployeeSchema);
app.use("/", async (req, res) => {
// await Department.remove({});
// await Department.create({
// name: "Fiocruz",
// location: "Presidência"
// }).then(console.log(`we are good`));
// await Department.create({
// name: "IASI",
// location: "Roma"
// }).then(console.log(`we are good`));
// await Employee.create({
// firstName: "Jorge",
// lastName: "Pires",
// department: await Department.findOne({ name: "Fiocruz" })
// });
// await Employee.create({
// firstName: "Marcelo",
// lastName: "Pires",
// department: await Department.findOne({ name: "IASI" })
// });
// Employee.findOne("")
// .populate("department", "name")
// .select("department")
// .then(result => {
// console.log(result);
// });
await Employee.findOne({ _id: "5e6e28ec480a9d32fc78c46b" }, (err, result) => {
console.log(result);
})
.populate("department", "name")
.select("department");
res.json({
departments: await Department.find(),
employees: await Employee.find(),
employeesWithDep: await Employee.find().populate("department", "name"),
justDepartment: await Employee.findOne({ _id: "5e6e28ec480a9d32fc78c46b" })
.populate("department", "name")
.select("department")
});
});
app.listen(3000, () => {
console.log("we are on port 3000");
});