How to query embedded documents in an embedded array mongodb

Question

I am starting out with mongodb and mongoose. This is what my db looks like

[
 {
  _id: "5fd0f98751e33831d8ef4899"
  date: "01/01/2020, 11:47:00 AM"
  groups: [
     {
       _id: "5fd0f98751e33831d8ef489a"
       name: "Eyob"
       profession: "doctor"
       posts: [
           { 
              _id: "5fd0f98751e33831d8ef489b"
              numberOfLikes: 16
              numberOfShares: "2 Shares"
           },
           { 
              _id: "5fd0f98751e33831d8ef489c"
              numberOfLikes: 26
              numberOfShares: "7 Shares"
           }
        
         ]
      },
      {
       _id: "5fd0f98751e33831d8ef489d"
       name: "Abel"
       profession: "teacher"
       posts: [
           { 
              _id: "5fd0f98751e33831d8ef489e"
              numberOfLikes: 16
              numberOfShares: "2 Shares"
           },
           { 
              _id: "5fd0f98751e33831d8ef489f"
              numberOfLikes: 26
              numberOfShares: "7 Shares"
           }    
         ]
      }

    ]

  },

  {
   _id: "5fd0f98751e33831d8ef489d"
   date: "01/02/2020, 11:47:00 AM"
   groups: [// an array of groups as the above one //]
  }
]

so for every groups array there is a group object that contains a posts array that contains a post object.('This might be confusing'). What I am trying to do is query a single post and also a single group using there unique ids. findById() returns null. Is there a way that I can query this objects using just there respective id's.

Answer 1

Try this, it should solve your issue.

(send a single-post _id to get your expected data)

const {id}=req.params;
YourDataModel.findOne({"groups.posts._id":id}, {"groups.posts._id.$":true})
.then(data=>data?res.send({
                     groupId:data.groups[0]._id, 
                     groupName:data.groups[0].name, 
                     post:data.groups[0].posts.filter(e=>e._id===id)[0]
            }): res.send("Not found!"))
.catch(err=>res.send(err))

You also can get all the posts of the group (relevant to that post) with the same code, just do res.send(data) or make necessary modification where necessary.