How do I increment a property of a subdocument in Mongoose? - node.js

Question

I am making a route in NodeJS using Mongoose which increments the rating of a subdocument of an object. I will post the models and route code below. When I execute the query in Postman, I get an empty json object back and a 400 error. This means somewhere in the query I am doing something wrong.
blogPost model
const BlogPostSchema = new Schema({
content: {
type: String,
validate: {
validator: (content) => content.length > 5,
message: 'Content must contain at least 6 characters.'
},
required: [true, 'Content must be filled in.']
},
rating: Number,
title: String,
user: { type: Schema.Types.ObjectId, ref: 'user' },
board: {type: Schema.Types.ObjectId, ref: 'board'},
comments: [commentSchema]
});
const BlogPost = mongoose.model('blogPost', BlogPostSchema);
module.exports = BlogPost;
comment schema
const CommentSchema = new Schema({
content: {
type: String,
validate: {
validator: (content) => content.length > 5,
message: 'Content must contain at least 6 characters.'
},
required: [true, 'Content must be filled in.']
},
user: { type: Schema.Types.ObjectId, ref: 'user' },
rating: Number
});
module.exports = CommentSchema;
NodeJS route
routes.put('/blogPosts/:id/comment/:idm', function(req, res) {
const blogPostId = req.param('id');
const commentId = req.param('idm');
BlogPost.findById(blogPostId)
.then((blogPost) => {
blogPost.comments.findByIdAndUpdate({_id: commentId}, {$inc: {rating: 1}});
})
.then((blogPost) => res.status(200).json({
'status': 'Comment rating is increased.'
}))
.catch((error) => res.status(400).json(error))
});
This is the response PostMan
All help is appreciated.

Answer 1

This was the error:
BlogPost.findById(blogPostId)
.then((blogPost) => {
blogPost.comments.findByIdAndUpdate({_id: commentId}, {$inc: {rating: 1}});
})
.then((blogPost) => res.status(200).json({
'status': 'Comment rating is increased.'
}))
Should be:
BlogPost.update({_id: blogPostId, 'comments._id': commentId}, {$inc:{'comments.$.rating':1}})
.then((blogPost) => res.status(200).json({
'status': 'Comment rating is increased.'
}))