Populating nested array with ObjectIDs - mongodb

Question

Trying to populate an array of ObjectID's within my schema. I've looked around at similar answers but it seems everyone is doing it slightly differently and I haven't been able to find a solution myself.
My schema looks like this:
var GameSchema = new Schema({
title: String,
description: String,
location: String,
created_on: { type: Date, default: Date.now },
active: { type: Boolean, default: true },
accepting_players: { type: Boolean, default: true },
players: [{
type: Schema.Types.ObjectId,
ref: 'User'
}],
admins: [{
type: Schema.Types.ObjectId,
ref: 'User'
}]
});
So far I've been trying to populate it like this, which obviously isn't working
exports.getAdmins = function(req, res) {
Game.findById(req.params.id)
.populate('admins')
.exec(function(err, game) {
return res.json(200, game.admins);
});
};
I hate to add to the list of population questions, but I've looked at many and haven't found a solution. Any help is greatly appreciated!
Edit:
Here's how I am adding admins to the document
// Add admin to game
exports.addAdmin = function(req, res) {
Game.findByIdAndUpdate(
req.params.id,
{ $push: { 'admins': req.params.user_id }},
function(err, game) {
if(err) { return handleError(res, err); }
if(!game) { return res.send(404); }
return res.json(200, game.admins);
});
};

Answer 1

Well I went back to mongoose documentation, and decided to change how I looked up a game by an ID and then populated the response.
Now my working function looks like this:
// Returns admins in a game
exports.getAdmins = function(req, res) {
Game.findById(req.params.id, function(err, game) {
if(err) { return handleError(res, err); }
if(!game) { return res.send(404); }
Game.populate(game, { path: 'admins' }, function(err, game) {
return res.json(200, game);
});
});
};
The issue I was having was that I was trying to call the .populate function directly with the .findById method, but that doesn't work because I found on mongoose's documentation the the populate method need the callback function to work, so I just added that and voila, it returned my User object.

Answer 2

to populate an array, you just have to put model name field after path field like this :
Game.findById(req.params.id)
.populate({path: 'admins', model: 'AdminsModel'})
.exec(function(err, game){...});
it works perfectly on my projects...