get array of objects where boolean is true - mongodb

Question

this is my collection
{
"_id": "bRu9ExERzz8PCDwRp",
"persian_title": "عنوان پارسی",
"english_title": "english title",
"price": 5000,
"offer_price": 2000,
"free_for_all": false,
"is_offer": false,
"author_id": "JH3hJGsuYFnRLFLWY"
"Seasons": [
{
"title": "intro",
"free_for_all": false,
"Episodes": [
{
"title": "first episode",
"length": "12",
"url": "0.mp4",
"free_for_all": true
},
{
"title": "second episode",
"length": "05",
"url": "1.mp4",
"free_for_all": false
}
]
}
]
}
i'm trying to get Seasons , episodes where free_for_all is true.
tried this but it doesn't work.
db.courses.find({_id:"bRu9ExERzz8PCDwRp"}, {
"Seasons": {
"$elemMatch": {
"Episodes": {
"$elemMatch": {
"free_for_all": true,
}
}
}
}
})
the result is just like this query :
db.courses.find({_id:"bRu9ExERzz8PCDwRp"})
how can i get only free seasons and episodes?

Answer 1

Your question is ambiguous regarding the desired outcome for free season with non-free episodes, and vice versa, free episodes in non-free seasons. So I'm assuming you want only episodes that are free and are part of a free season. That's what the following will give you (not tested):
_.reduce(db.courses.findOne({_id:"bRu9ExERzz8PCDwRp"}).Seasons, function(all, s) {
if (s.free_for_all) {
all = _.reduce(s.Episodes, function(memo, e) {
if (e.free_for_all) memo.push(e);
return memo;
}, all);
}
return all;
}, []);
If you want all episodes that are free or part of a free season:
_.reduce(db.courses.findOne({_id:"bRu9ExERzz8PCDwRp"}).Seasons, function(all, s) {
if (s.free_for_all) {
all = all.concat(s.Episodes);
} else {
all = _.reduce(s.Episodes, function(memo, e) {
if (e.free_for_all) memo.push(e);
return memo;
}, all);
}
return all;
}, []);