Mongoose do not populate objectid in an objectid of array - node.js

Question

THIS PROBLEM IS A LITTLE LONGER. SO I TYPED BOLD THE CRITICAL INFORMATIONS FOR YOU.
I develop a project like stackoverflow. I have 4 databases which are:
problems
users
solutions
comments
I referrenced these schemas each other. Here is the Schemas:
Problem Schema
const problemSchema = new mongoose.Schema({
title: {
type: String,
required: [true, 'You have to enter a title']
},
content: {
type: String,
required: [true, 'You have to enter a content']
},
createdAt: {
type: Date,
default: Date.now()
},
slug: {
type: String
},
solution: [
{
type: mongoose.Schema.Types.ObjectId,
ref: 'Solution'
},
],
comment: [
{
type: mongoose.Schema.Types.ObjectId,
ref: 'Comment'
}
],
votes: {
type: Number,
default: 0
},
views: {
type: Number,
default: 0
},
user: {
type: mongoose.Schema.Types.ObjectId,
required: true,
ref: 'User'
}
})
module.exports = mongoose.model('Problem', problemSchema)
User Schema:
const userSchema = new mongoose.Schema({
name: {
type: String,
required: true
},
email: {
type: String,
required: [true, 'You have to enter an email'],
unique: true,
match: [
/^([\w-\.]+#([\w-]+\.)+[\w-]{2,4})?$/,
'Please provide a valid email address.'
]
},
password: {
type: String,
required: [true, 'You have to enter a password'],
minlength: [6, 'Your password cannot be less than 6 character.'],
select: false
},
role: {
type: String,
default: 'user',
enum: ['user', 'admin']
},
createdAt: {
type: Date,
default: Date.now()
},
about: {
type: String
},
place: {
type: String
},
age: {
type: Number
},
blocked: {
type: Boolean,
default: false
},
problem: [
{
type: mongoose.Schema.Types.ObjectId,
ref: 'Problem'
},
],
solution: [
{
type: mongoose.Schema.Types.ObjectId,
ref: 'Solution'
}
],
comment: [
{
type: mongoose.Schema.Types.ObjectId,
ref: 'Comment'
}
]
})
and Comments Schema:
const commentSchema = new mongoose.Schema({
content: {
type: String,
required: [true, 'You have to enter a content']
},
createdAt: {
type: Date,
default: Date.now()
},
isFunctional: {
type: Boolean,
default: false
},
user: {
type: mongoose.Schema.Types.ObjectId,
required: true,
ref: 'User'
},
problem: {
type: mongoose.Schema.Types.ObjectId,
ref: 'Problem'
},
})
module.exports = mongoose.model('Comment', commentSchema)
In my project, I send problems into MongoDB. Then I send comment. After save comments, I add these comments into problems and user DB with a function.
function that comments are saved in DB:
const Comment = require('../models/comment/Comment')
const Problem = require('../models/problem/Problem')
const User = require('../models/user/User')
const asyncErrorWrapper = require('express-async-handler')
const addCommentToProblem = asyncErrorWrapper(async (req, res, next) => {
const {content, problemId} = req.body
const newComment = await Comment.create({
content: content,
problem: problemId,
user: req.user.id,
})
const problemOfComment = await Problem.findByIdAndUpdate(problemId, {
$push: { comment: newComment._id }
})
const userOfComment = await User.findByIdAndUpdate(req.user.id, {
$push: { comment: newComment._id }
})
})
Okey everything is so far so good. The problem comes here. When I try to get a problem, I populate some fields for example user fields. So I can add user information in this detail of problem. When populate user and comment in problem schema, it sends me the data. Still, we're ok. But when I try to get user field in comments, it doesn't populate user. It turns just objectId of user information.
Here is the function that I get problem:
const getAProblem = asyncErrorWrapper(async (req, res, next) => {
const {id} = req.params
const problems = null
await Problem.findByIdAndUpdate(id, {
$inc: { views: 1 }
}, { new: true })
.populate('user') ==> THIS LINE WORKS
.populate('comment') ==> THIS LINE WORKS
.populate('comment.user') ==> THIS LINE DOES NOT WORK
.exec(function(err, post) {
if(err) {
console.log(err)
}
res
.status(200)
.json({
success: true,
data: post
})
});
})
Thanks for reading and your patience. Any help will be appreciated.

Answer 1

See doc at https://mongoosejs.com/docs/populate.html
And try this way.
const getAProblem = asyncErrorWrapper(async (req, res, next) => {
const {id} = req.params
const problems = null
await Problem.findByIdAndUpdate(id, {
$inc: { views: 1 }
}, { new: true })
.populate('user') ==> THIS LINE WORKS
.populate({
'path': 'comment',
'populate': {
'path':'user'
}
})
.exec(function(err, post) {
if(err) {
console.log(err)
}
res
.status(200)
.json({
success: true,
data: post
})
});
})