Mongoose sub-documents inside nested object - node.js

Question

I have a schema which uses multiple fields as reference to other collections in the database.
Everything seems to work fine except for a sub-document which is present in a nested object.
When I try to add the document as a reference to that particular key (role) in a nested object (metadata), instead of the ObjectId the entire object gets saved.
This is my schema:
class Metadata {
// THIS DOES NOT WORK FINE AND IT STORES THE COMPLETE OBJECT
// AND ALSO EMPTY ARRAY IS NOT CREATED UPON THE DOCUMENT CREATION
// WHICH IS DEFAULT BEHAVIOUR OF MONGOOSE
#Prop({
ref: 'Role',
type: [mongoose.Schema.Types.ObjectId]
})
roles: Role[];
}
#Schema({...})
export class User {
#Prop()
name: string;
#Prop()
password: string;
// This works fine and it only stores the ObjectId
#Prop({
ref: 'Favourite',
type: [mongoose.Schema.Types.ObjectId]
})
favourties: Favourite[]
#Prop({type: Metadata})
metadata: Metadata;
// WHEN THE SAME IS REMOVED OUT OF METADATA OBJECT, IT WORKS
// FINE AND STORES ONLY OBJECT ID
#Prop({
ref: 'Role',
type: [mongoose.Schema.Types.ObjectId]
})
roles: Role[];
}
I'm using "#nestjs/mongoose": "^9.2.1" and "mongoose": "^6.8.2".

Answer 1

If you want to embed a reference to the document in metadata collection, you should refer it by the objectId in the User document itself.
#Schema({collection: 'metadata'})
class Metadata {
#Prop({
ref: 'Role',
type: [mongoose.Schema.Types.ObjectId]
})
roles: Role[];
}
#Schema({...})
export class User {
#Prop()
name: string;
#Prop()
password: string;
#Prop({
ref: 'Favourite',
type: [mongoose.Schema.Types.ObjectId]
})
favourties: Favourite[]
#Prop({
ref: 'Metadata',
type: [mongoose.Schema.Types.ObjectId]
})
metadata: Metadata;
}