How to update a text within a nested model - MERN stack - node.js

Question

I have just started learning the MERN stack and I am having trouble updating a text within a model with Express/Node. I tried to look for help and accessed Update a model within a model
How to Nest Models within a Model but they weren't quite what I was looking for.
I am working with 2 models, with the comments model embedded within the cats models like so. This is the comment model
const mongoose = require("mongoose");
const Schema = mongoose.Schema;
const commentSchema = new Schema(
{
user_id: { type: String, required: true },
cat_id: { type: String, required: true },
text: {
type: String,
min: [3, "Comment cannot be too short"],
},
email: { type: String, required: true },
},
{ timestamps: true }
);
const Comment = mongoose.model("Comment", commentSchema);
module.exports = Comment;
And this comment model is within the cat models
const mongoose = require("mongoose");
const Schema = mongoose.Schema;
const Comment = require("./comments.js");
const catSchema = new Schema(
{
name: {
type: String,
required: true,
unique: true,
min: [2, "Cat name minimum of 2 characters."],
},
description: { type: String, required: true },
image: { type: String },
gender: { type: String, required: true },
cage: { type: String, required: true },
adoptable: { type: String, required: true },
comments: [Comment.schema],
},
{ timestamps: true }
);
const Cat = mongoose.model("Cat", catSchema);
module.exports = Cat;
In my controller, when I update a comment, I need to update the respective comment inside the cat model too, but I'm not able to do so. I tried targeting the particular cat, foundCat, and I can't access the comment with foundCat.comments.id(req.params.id)
Strangely enough, when I console log "foundCat.comments.id", it tells me that this is a function? So I don't know why I can't access and update that text...
Here is my code for updating the comment: Note! The part with issue is located at the end, look for "Cat.findOne"
// For updating comment
const updateComment = async (req, res) => {
// if there is no req.body, return error
if (!req.body) {
return res.status(400).json({
success: false,
error: "You must provide a body to update",
});
}
// req.body exists, so find the comment by id and then update
Comment.findOne({ _id: req.params.id }, (err, comment) => {
if (err) {
return res.status(404).json({
err,
message: "Comment not found!",
});
}
console.log(req.body);
// update the comment details
comment.text = req.body.text;
// save the updated comment
comment
.save()
.then(() => {
// return json response if successful
return res.status(200).json({
success: true,
id: comment._id,
message: "Comment updated!",
});
})
.catch((error) => {
return res.status(404).json({
error,
message: "Comment not updated!",
});
});
// now update the comment entry for the cat too
Cat.findOne({ _id: comment.cat_id }, (err, foundCat) => {
console.log("This doesnt work", foundCat.comments.id(req.params.id));
foundCat.save((err, updatedCat) => {
console.log(updatedCat);
});
});
});
};
Example of the comments within a cat:

Answer 1

You should update the cat instance once the comment has been fetched.
Try to change your code like this (using async wait):
const updateComment = async (req, res) => {
// if there is no req.body, return error
if (!req.body) {
return res.status(400).json({
success: false,
error: 'You must provide a body to update',
});
}
try {
// req.body exists, so find the comment by id and then update
const comment = await Comment.findById(req.params.id);
if (!comment) {
return res.status(404).json({
err,
message: 'Comment not found!',
});
}
// update the comment details
comment.text = req.body.text;
// save the updated comment
await comment.save();
// now update the comment entry for the cat too
const cat = await Cat.findById(comment.cat_id);
const otherCatComments = cat.comments.filter((c) => c._id !== comment._id);
cat.comments = [...otherCatComments, comment];
await cat.save();
res.status(200).json({
success: true,
id: comment._id,
message: 'Comment updated!',
});
} catch (err) {
res.status(404).json({
error,
message: 'Comment not updated!',
});
}
};

Answer 2

Luca, thank you! That was extremely helpful and I can see the appended comment added to the cats comment array. Now the only thing is the cats.comment.filter isn’t quite working as intended, as the otherCatsComments still includes all the comments. I had to do a little digging in the code and I managed to console log the id, which returns “_id: new ObjectId("617d57719e815e39f6049452"),”
I tried changing it to
const otherCatComments = cat.comments.filter((c) => c._id !== `new ObjectId("${comment._id}")`);
const otherCatComments = cat.comments.filter((c) => c._id !== ` new ObjectId("${comment._id}")`);
const otherCatComments = cat.comments.filter((c) => c._id !== `ObjectId("${comment._id}")`);
But they all don’t seem to work, so I had to do a deep de-bugging and turns out my code is off for some things! I’ll just add them here in case anyone bumps into this issue in the future.
First off, my comment id was different from the comment id within my cats model. For reference, here is my create comment model (I modified it to use the async/await + try/catch block as recommended by Luca:
const createComment = async (req, res) => {
// if there is no req.body, return error
if (!req.body) {
return res.status(400).json({
success: false,
error: "You must provide a comment",
});
}
try {
// req.body exists, so make a new comment
const comment = new Comment(req.body);
await comment.save();
// now add comment to cat
Cat.findById(req.params.id, (err, foundCat) => {
// Append the comment to the cat
foundCat.comments.push(comment);
foundCat.save();
});
// somehow, if the new comment doesn't exist, return error
if (!comment) {
return res.status(400).json({ success: false, error: err });
}
// success!
res.status(201).json({
success: true,
id: comment._id,
message: "Comment created!",
});
} catch (err) {
return res.status(400).json({
err,
message: "Comment not created!",
});
}
};
Note the part where I add the comments in the cat:
At first it was
foundCat.comments.push(req.body);
but this would generate a comment id in the cat that would be different from the comment id in the comment. so req.body is changed to comment.
Once that was fixed, I tried the original code by Luca, but it still didn’t work. My workaround was to not use the filter, and just delete the old comment and then add in the new comment.
Code here:
const updateComment = async (req, res) => {
// if there is no req.body, return error
if (!req.body) {
return res.status(400).json({
success: false,
error: "You must provide a body to update",
});
}
try {
// req.body exists, so find the comment by id and then update
const comment = await Comment.findById(req.params.id);
if (!comment) {
return res.status(404).json({
err,
message: "Comment not found!",
});
}
// update the comment details
comment.text = req.body.text;
// save the updated comment
await comment.save();
// now update the comment entry for the cat too
const cat = await Cat.findById(comment.cat_id);
// remove the old, non-updated comment first
cat.comments.id(comment._id).remove();
// now add in the updated comment
cat.comments.push(comment);
await cat.save();
res.status(200).json({
success: true,
id: comment._id,
message: "Comment updated!",
});
} catch (err) {
res.status(404).json({
error,
message: "Comment not updated!",
});
}
};