How do I implement Mongo DB query to find key in all objects inside an array? - mongodb

Question

After looking into several books, the mongo db reference and other stackoverflow questions, I can't seem to get this query right.
I have the following data structure:
Posts collection:
{
"content" : "...",
"comments" : [
{
"author" : "joe",
"score" : 3,
"comment" : "nice post"
},
{
"author" : "bob",
"score" : 5,
"comment" : "nice"
}]
}
What I'm trying to get is all of the author names inside each of the objects of the array inside a Handlebars helper, not in the console. So I would have something like:
...
commentsAuthors: function() {
return Collection.find({...});
}
UPDATE:
I decided to reduce my array to only an Array of strings which I later queried like this:
New Array:
{
"content" : "...",
"comments" : ["value1", "value2", "..."]
}
MeteorJS Handlebars helper:
Template.courseEdit.helpers({
comments: function(){
var cursor = Courses.find({"_id": "8mBATtGyyWsGr2PwW"}, {"comments": 1, "_id": 0}).fetch();
return cursor.map(function(doc, index, cursor){
var comment = doc.comments;
console.log(comment);
return comment;
});
}
});
At this point, I'm able to render the Whole array in my view with this {{#each}}...{{/each}}:
<ul class="list-unstyled">
{{#each comments}}
<li class="pl-14"><i class="icon-checkmark"></i> {{this}}</li>
{{/each}}
</ul>
However I'm getting the whole array in one single list item.
How can I create a separate list item for each of my Array strings?
Thanks in advance.

Answer 1

Should be as easy as (replace posts with your collection name):
db.posts.distinct("comments.author")
Or if you need it per post:
db.posts.aggregate([
{ $unwind: "$comments" },
{ $group: { "_id": "$_id", authors: { "$addToSet": "$comments.author"} } }
])

Answer 2

You can get only certain fields by limiting fields
db.collection.find({"content" : "..."},{"comments.author":1})