Return Array of Populated Objects in Mongoose - mongodb

Question

I have a DB for a forum with 3 collections: Threads, Posts, Comments.
I have a GET request to return an individual forum thread that populates each thread with user's posts, and each user post with any comments that were made on it which is working as shown below:
router.get('/:id', (req, res) => {
Threads
.findById(req.params.id)
.lean()
.populate({path: 'posts'})
.exec(function(err, docs){
var options = {
path: 'posts.comments',
model: 'comments'
};
if(err) return res.json(500);
Threads.populate(docs, options, function(err, thread){
res.json(thread);
})
})
})
When this GET request is made it will return a forum thread like so:
{
"_id": "5924ad549a08ed4e70a9c89f",
"title": "Testing Full Schemas",
"author": "Mongoose",
"content": "Schema Content",
"posts": [
{
"_id": "5924ad999a08ed4e70a9c8a0",
"content": "New Schema Post",
"user": "Mongodb",
"comments": [
{
"_id": "5924ae489a08ed4e70a9c8a1",
"comment": "New Schema Content",
"user": "Matt",
"likes": 0,
"created": "2017-05-25T12:41:58.319Z"
}
]
}
Now I need a GET request to return an array of ALL threads (router.get('/')) with each threads posts and comments to be populated. I tried to replace:
Threads
.findById(req.params.id)
with
Threads
.find(req.params.id)
but it is not working. Does anyone have an idea of how this could be accomplished?

Answer 1

To return all the threads, simply use find without any match condition in it.
Also, populate posts and 'posts.comment' in the find query itself, you don't need to do it in the callback of the find.
use population across multiple levels
**Try this:
Threads.find({})
.populate({
path:'posts',
populate :{
path : comments
}
})
.exec(function(err,docs){
//docs is the array of all the Threads, with posts and comments populated within it
})
Read Mongoose Documentation on Populate and Nested Population for detailed information. ( Search for Populating across multiple levels)

Answer 2

findById and findOne returns a single document, where find returns a cursor. Once you go through the cursor of find, you are at the end, and there are no more documents.
Using find query:-
ModelName.find({_id:req.params.id})
.populate({
path:'posts',
populate :{
path : comments
}
},(error,data)=>{
if(error){
res.json(error);
}
else{
res.json(data);
}
})
Using findById query:-
ModelName.findById(req.params.id)
.populate({
path:'posts',
populate :{
path : comments
}
},(error,data)=>{
if(error){
res.json(error);
}
else{
res.json(data);
}
})