Create Mongoose Find and populate from multiple tables with property set - node.js

Question

I'll be grateful for help with Mongoose. I have 3 tables: (Users)Table of users, (Animals)table of animals and table AnimalComments. So (AnimalComments)table reference users and animals.
const schemaComment = new mongoose.Schema({
userRef: {
type: mongoose.Schema.Types.ObjectId,
ref: 'User'
},
animalRef: {
type: mongoose.Schema.Types.ObjectId,
ref: 'Animal'
},
content: {
type: String
}
});
const schemaAnimal = new mongoose.Schema({
name: {
type: String
},
isCommentedByMe: {
type : Boolean,
default: false
},
commentCount: {
type : Number,
default: 0
}
});
What I want: I have animals. Users can add comment to animal. When user comment animal his comment is added to table AnimalComments where is stored userRef (userId), animalRef (animalId) and user comment text. Then in request response I want return all animals from table Animals but I need update property commentCount and isCommentedByMe based on value from table AnimalComments.
Response from table Animals:
{
"animals": [
{
"isCommentedByMe": false,
"commentCount": 0,
"name": "Jessica",
"userRef": {
"id": "5dc9bdf3dd5cae00177e184d"
},
"id": "5dcedd48368e9800176f2ef3"
}
]
}
Response from table Users:
{
"users": [
{
"name": "Jony Cash",
"id": "5dc9bdf3dd5cae00177e184d"
}
]
}
Response from table AnimalComments:
{
"comments": [
{
"userRef": "5dc9bdf3dd5cae00177e184d",
"animalRef": "5dcedd48368e9800176f2ef3",
"content": "Sample text"
}
]
}
I want result for exmaple:
{
"animals": [
{
"isCommentedByMe": true,
"commentCount": 4,
"name": "Jessica",
"userRef": {
"id": "5dc9bdf3dd5cae00177e184d"
},
"id": "5dcedd48368e9800176f2ef3"
}
]
}

Answer 1

You don't need to keep isCommentedByMe and commentCount fields in animal schema.
And you need to be able access comments from your animals. But in animal schema there is no field to make that connection. So we need to use virtual population.
So your animal schema must be like this:
const schemaAnimal = new mongoose.Schema(
{
name: {
type: String
}
},
{
toJSON: { virtuals: true },
toObject: { virtuals: true }
}
);
// Virtual populate
schemaAnimal.virtual("comments", {
ref: "Comment", //must be changed to the name you used for Comment model.
foreignField: "animalRef",
localField: "_id"
});
Now, we can use the following code to populate the comments.
router.get("/animals", async (req, res) => {
const animals = await Animal.find({}).populate("comments");
res.send(animals);
});
This will give you a result like this:
[
{
"_id": "5dd66c73069f88614c12b394",
"name": "Animal 1",
"__v": 0,
"comments": [
{
"_id": "5dd66cfd069f88614c12b39a",
"userRef": "5dd66b54c5195127ec5a1b82",
"animalRef": "5dd66c73069f88614c12b394",
"content": "User 1 - Animal 1",
"__v": 0
},
{
"_id": "5dd66d30069f88614c12b39d",
"userRef": "5dd66b71c5195127ec5a1b83",
"animalRef": "5dd66c73069f88614c12b394",
"content": "User 2 - Animal 1",
"__v": 0
}
],
"id": "5dd66c73069f88614c12b394"
},
{
"_id": "5dd66c7d069f88614c12b395",
"name": "Animal 2",
"__v": 0,
"comments": [
{
"_id": "5dd66d09069f88614c12b39b",
"userRef": "5dd66b54c5195127ec5a1b82",
"animalRef": "5dd66c7d069f88614c12b395",
"content": "User 1 - Animal 2",
"__v": 0
}
],
"id": "5dd66c7d069f88614c12b395"
},
{
"_id": "5dd66c88069f88614c12b396",
"name": "Animal 3",
"__v": 0,
"comments": [
{
"_id": "5dd66d46069f88614c12b39e",
"userRef": "5dd66b71c5195127ec5a1b83",
"animalRef": "5dd66c88069f88614c12b396",
"content": "User 2 - Animal 3",
"__v": 0
}
],
"id": "5dd66c88069f88614c12b396"
}
]
To convert this result to what you wanted, we can use map like this:
Please note that, you need to set loggedInUserId variable to logged in user's id.
router.get("/animals", async (req, res) => {
const loggedInUserId = "5dd66b54c5195127ec5a1b82";
const animals = await Animal.find({}).populate("comments");
const result = animals.map(animal => {
return {
id: animal._id,
name: animal.name,
isCommentedByMe:
animal.comments.filter(c => c.userRef.toString() === loggedInUserId)
.length > 0,
commentCount: animal.comments.length
};
});
res.send(result);
});
The result will be like this:
[
{
"id": "5dd66c73069f88614c12b394",
"name": "Animal 1",
"isCommentedByMe": true,
"commentCount": 2
},
{
"id": "5dd66c7d069f88614c12b395",
"name": "Animal 2",
"isCommentedByMe": true,
"commentCount": 1
},
{
"id": "5dd66c88069f88614c12b396",
"name": "Animal 3",
"isCommentedByMe": false,
"commentCount": 1
}
]
And the answer for the question in the comments is: (how to reference User)
const animals = await Animal.find({}).populate({
path: "comments",
model: Comment,
populate: [
{
path: "userRef",
model: User
}
]
});
This will give you the userRef like this:
[
{
"_id": "5dd66c73069f88614c12b394",
"name": "Animal 1",
"__v": 0,
"comments": [
{
"_id": "5dd66cfd069f88614c12b39a",
"userRef": {
"_id": "5dd66b54c5195127ec5a1b82",
"name": "User 1",
"__v": 0
},
"animalRef": "5dd66c73069f88614c12b394",
"content": "User 1 - Animal 1",
"__v": 0
},
{
"_id": "5dd66d30069f88614c12b39d",
"userRef": {
"_id": "5dd66b71c5195127ec5a1b83",
"name": "User 2",
"__v": 0
},
"animalRef": "5dd66c73069f88614c12b394",
"content": "User 2 - Animal 1",
"__v": 0
}
],
"id": "5dd66c73069f88614c12b394"
},
{
"_id": "5dd66c7d069f88614c12b395",
"name": "Animal 2",
"__v": 0,
"comments": [
{
"_id": "5dd66d09069f88614c12b39b",
"userRef": {
"_id": "5dd66b54c5195127ec5a1b82",
"name": "User 1",
"__v": 0
},
"animalRef": "5dd66c7d069f88614c12b395",
"content": "User 1 - Animal 2",
"__v": 0
}
],
"id": "5dd66c7d069f88614c12b395"
},
{
"_id": "5dd66c88069f88614c12b396",
"name": "Animal 3",
"__v": 0,
"comments": [
{
"_id": "5dd66d46069f88614c12b39e",
"userRef": {
"_id": "5dd66b71c5195127ec5a1b83",
"name": "User 2",
"__v": 0
},
"animalRef": "5dd66c88069f88614c12b396",
"content": "User 2 - Animal 3",
"__v": 0
}
],
"id": "5dd66c88069f88614c12b396"
}
]