ExpressJs - Mongoose: Delete documents with Many To Many relationship - express

Question

I've two Models, Post and Tag with Many To Many relationships.
Post Schema:
const postSchema = new Schema(
{
user: {
type: Schema.Types.ObjectId,
ref: 'User',
required: [true, 'A post must belong to a user.'],
},
title: {
type: String,
unique: [true, 'A Post already exists with this title.'],
required: [true, 'A Post must have a title.'],
},
slug: { type: String, unique: true },
body: { type: String, required: [true, 'A Post must have a body.'] },
coverImage: String,
images: Array,
isDraft: { type: Boolean, default: false },
isPublished: { type: Boolean, default: false },
tags: [{ type: Schema.Types.ObjectId, ref: 'Tag' }],
},
{
timestamps: { currentTime: () => Math.floor(Date.now() / 1000) },
toJSON: { virtuals: true },
toObject: { virtuals: true },
}
)
Tag Schema:
const tagSchema = new Schema(
{
title: { type: String, required: true },
slug: { type: String },
posts: [{ type: Schema.Types.ObjectId, ref: 'Post' }],
},
{
timestamps: { currentTime: () => Math.floor(Date.now() / 1000) },
toJSON: { virtuals: true },
toObject: { virtuals: true },
}
)
Now I want to remove all the references of the Posts from the Tag documents when a Post is deleted.
I'm trying to the following remove middleware in the Post model but it is not working. The post get deleted but the reference still there on the Tag documents.
postSchema.pre('remove', function (next) {
var post = this
post
.model('Tag')
.update(
{ posts: { $in: post.tags } },
{ $pull: { posts: post._id } },
{ multi: true },
next
)
})

Answer 1

After trying many times I finally fired out what wrong I was doing. Following the fix I made to make it work:
In Post Controller I was previously doing this:
const post = await Post.findByIdAndDelete(req.params.id)
Which I changed to:
const post = await Post.findById(req.params.id)
await post.remove()
And in Post Model:
postSchema.pre('remove', async function (next) {
await this.model('Tag').updateMany(
{ posts: this._id },
{ $pull: { posts: this._id } },
{ multi: true },
next
)
})