How should you query a collection via nested arrays in mongodb (Meteor)? - mongodb

Question

I'm dont think that this is a Meteor specific question, but rather around mongo and building mongo queries.
If I have the following structure,
{
username : someName,
contacts : [
{
userid : asdfae33rtqqxxx,
name : contactName,
status : friend
}
{
userid : asdfae33rtqqxxx,
name : anotherName,
status : pending
}
{
userid : asdfae33rtqqxxx,
name : contactName,
status : blocked
}
]
}
How could I pass in values from this array into a query against the users collection, to a) get the users in this array, or b) get all users in this array from the users collection with a particular status.
If this is not possible, how should I adjust my schema in order to make these sorts of queries possible?

Answer 1

This function will return a Meteor.users cursor based on an array of contacts and an optionally required status:
var usersByContacts = function(contacts, requiredStatus) {
var userIds = _.chain(contacts)
.map(function(c) {
if (requiredStatus) {
if (c.status === requiredStatus)
return c.userid;
} else {
return c.userid;
}
})
.compact()
.value();
return Meteor.users.find({_id: {$in: userIds}});
};
You can use it like this:
var users1 = usersByContacts(thing.contacts);
var users2 = usersByContacts(thing.contacts, 'pending');
This assumes thing has the schema referenced in your question. Also note that if you find this is a common pattern in your code, you should consider turning usersByContacts into a transform.