Styjun

So I have this Mongoose Schema:

var mongoose = require('mongoose');
var Schema = mongoose.Schema;

var CommentSchema = new Schema(
 body: type: String, required: true, max: 2000,
 created: type: Date, default: Date.now ,
 flags: type: Number, default: 0,
 lastFlag: type: Date, default: Date.now(),
 imageBanned: type: Boolean, default: false,
 fileName: type: String, default: ""
, 
 writeConcern: 
 w: 0,
 j: false,
 wtimeout: 200
 
);

var PostSchema = new Schema(
 body: type: String, required: true, max: 2000,
 created: type: Date, default: Date.now ,
 flags: type: Number, default: 0,
 lastFlag: type: Date, default: Date.now(),
 fileName: type: String, default: "",
 imageBanned: type: Boolean, default: false,
 board: type: String, default: "",
 comments: [ type: Schema.Types.ObjectId, ref: 'Comment' ]
, 
 writeConcern: 
 w: 0,
 j: false,
 wtimeout: 200
 
);


var Post = mongoose.model('Post', PostSchema);
var Comment = mongoose.model('Comment', CommentSchema)

module.exports = Post, Comment

And I'm trying to query a Comment inside the comment array in post.

This is the endpoint I'm trying:

router.post('/flagComment', (req, res, next)=>
 console.log('inside /flagComment')
 console.log('value of req.body: ', req.body)
 model.Post.findOne("comments._id": req.body.id).exec((err, doc)=>
 if(err)
 console.log('there was an error: ', err)
 
 console.log('the value of the found doc: ', doc)
 res.json(dummy: 'dummy')
 )
)

However, this gives the following terminal output:

value of req.body: id: '5c9bd902bda8d371d5c808dc' 
the value of the found doc: null

That's not correct...I've verified the ID is correct - why is the comment doc not being found?

EDIT:

I've attempted this solution (Can't find documents searching by ObjectId using Mongoose) by setting the objectID like this:

var ObjectId = require('mongoose').Types.ObjectId; 

router.post('/flagComment', (req, res, next)=>
 console.log('inside /flagComment')
 console.log('value of req.body: ', req.body)
 console.log('value of objid req id : ', ObjectId(req.body.id))
 model.Post.find("comments._id": ObjectId(req.body.id)).exec((err, doc)=>
 if(err)
 console.log('there was an error: ', err)
 
 console.log('the value of the found doc: ', doc)
 res.json(dummy: 'dummy')
 )
)

And I get the following terminal output:

value of req.body: id: '5c9bd902bda8d371d5c808dc' 
value of objid req id : 5c9bd902bda8d371d5c808dc
the value of the found doc: []

So, this is not yet a solution although it appears to be better than what I had.

You aren't querying for an ObjectId, no matter how much you think you are. You are querying for the ObjectId encoded as a hexidecial string, which is not the same thing. Properly typecast and you will likely have far more success.

Edited to elaborate, from a mongo (JS) REPL shell:

> // Omitting the _id, or generating a new one, are equivalent during insert.
> db.foo.insert(_id: ObjectId())
WriteResult( "nInserted" : 1 )

> db.foo.find() // As expected, we get back our _real_ ObjectId value.
 "_id" : ObjectId("5c9cfab873724727778c0730") 

> // Can we "insert the record again" using a string version of the ID?
> db.foo.insert(_id: "5c9cfab873724727778c0730")
WriteResult( "nInserted" : 1 ) // Sure as heck can! No unique violation!

> db.foo.find() // Because THESE ARE NOT THE SAME
 "_id" : ObjectId("5c9cfab873724727778c0730") 
 "_id" : "5c9cfab873724727778c0730" 

After our IRC discussion, there seems to be difficulty in understanding the "searchable terms" in the answers you are being given. Search here on StackOverflow (or Google, or DDG) for "mongoose typecast ObjectId" (without quotes; or just "mongoose ObjectId"…) and you will find many answers, as this is a particularly common problem for Mongoose users.

Once try checking with populating the reference data first and then querying on the _id of the comment.

*Get the post id also from front end in addition to comment id, in that way it will be easier.

Post.findOne(_id:'postId')
.populate(
 path : 'comment',
 match : _id : 'commentId' 
)
.exec(...);