MongoDB - Meteor : Update, add and delete an element from an array - mongodb

Question

I am trying to select a specific element in an nested array in a hash like so.
post:{
_id,
comments:[{
comment_id:post.comments.length + 1,
comment: "hello world",
user_id:Meteor.userId()}]
}
My ultimate goal is to be able to add/edit/delete the nested comment by comment_id but I am having trouble trying to select the element I need in the first place.

Answer 1

If you only have comments in your post object you should only have a comments array like this:
Posts {
_id: String;
comments: [];
}
And to delete a comment by his id :
Posts.update({_id: postId, "comments.comment_id" : "commentIdToDelete"},
{ $pull:{"comments": {"comment_id": "commentIdToDelete"}}})
To update a comment by his id :
Posts.update({_id: postId, "comments.comment_id" : "commentIdToUpdate"},
{ $set:{"comments.$.comment": "A new comment"}})
UPDATE
In order to add a comment in the comments array we have to initialiaze the post document (if it's not already done):
Posts.insert({
comments: []
});
Now we have to retrieve the comments array size of the post to update:
let lengthComments = Posts.findOne({_id: postIdToUpdate}).comments.length;
And finally we can add a comment in the comments array:
Posts.update({_id: postIdToUpdate}, {
$push: {
"comments": {
"comment_id": lengthComments + 1,
"comment": "My comment",
"user_id": Meteor.userId(),
}
}
});