How to update in nested schema in mongodb? - mongodb

Question

I am working on meteor. I am trying to make blog with commmenting system.For post insertion my schema is this:
Posts.insert({
post:post,
author:username,
date:date,
createdAt:new Date(),
comment:{
commentBy:'',
commentMsg:''
},
userId:Meteor.userId()
})
At first the comment section will be blank. when user comment on particular post then comment section is filled.
I am trying to update this schema:
Posts.update(thisPost,{$addToSet:{comment.commentedBy:Name,comment.commentMsg:post}});
But its not working.How to do it right way??

Answer 1

for entering multiple comments the field should be an array.
comments:[{
Commentedby:String,
CommentedMsh:string
}]
You can either use $addtoset or $push,
db.update({_id:post._id},{$push:{comments:newComment}})
OR
db.update({_id:post._id}, { $addToSet: { comments : comment });

Answer 2

I think you need to put quotes around any dot references, like this:
Posts.update(thisPost,{$addToSet:{"comment.commentedBy":Name,"comment.commentMsg":post}});
The reason is because if you don't, your compiler will try and do object references locally, which is not what you want, if you pass it as a string, then Mongo will do it as expected.

Answer 3

There are two issues that I could find in your provided information.
First is that the comment property should be an array/collection, so you should initiate it as following (renamed to comments):
Posts.insert({
...
comments:[],
...
})
And second, and most important to answer you question, according to the documentation the first parameter on update should be either a selector, a ObjectID or a string id.
https://docs.meteor.com/api/collections.html#Mongo-Collection-update
So your update should look like this:
var comment = { commentBy: 'user-id', commentMsg: 'le-message' }
Posts.update(post._id, { $addToSet: { comments : comment });