Return a subdocument based on one of it's properties using mongoose

Question

Using mongoose, I want to search for subdocuments that have a certain property and return the most recent one.

// the relevant part of the user schema
id: String,
__history__: {
    reply: []
}

// the components of a 'reply' (not defined by a schema)
id: String,
createdAt: Date,
props {
    tipID: String
}

Given a specific user id, I want to search their reply[]s for replies that have a tipID in their props. I then want to return the tipID for the reply that has the most recent createdAt.

I'm new to - well - coding in general. Would love any pointers on how best to tackle this.

score 1 · Answer 1 · edited May 23 '17 at 12:03

1

This is a duplicate question of Mongoose - finding subdocuments by criteria

For your specific question, the trick with mongoose subdocuments is twofold:

a) avoid nesting within subdocuments if you can, i.e. do not nest your attributes within propId rather put those attributes straight into the reply, whatever they may be.

b) use $elemMatch as suggested in the duplicate answer I quoted above. This will make sure that mongoDb finds the right documents, since mongoDb recognises {a:1,b:2} and {b:2,a:1} as two different subdocuments.

edited May 23 '17 at 12:03

Community

1
1

answered Nov 18 '15 at 21:06

Ron Wertlen

830
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I should have been more clear - the 'reply' isn't a schema defined subdocument. Trying the $elemMatch approach return an error for me. – Michael Lewkowitz Nov 19 '15 at 16:05

score 1 · Answer 2 · answered Nov 18 '15 at 21:07

1

If you're only finding one document, then organize the replies something like this..

// find your doc by ID
user.findOne({ id: id }, function(err, doc) {
    // sort replies by createdAt date
    var replies = _.sortBy(doc.reply, function(reply) {
        return reply.createdAt.getTime(); // convert to seconds from jan 1, 1970
    });

    return replies[0].props.tipId;
})

answered Nov 18 '15 at 21:07

Brant

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Accept the answer please? – Brant Nov 19 '15 at 16:22
it pointed me in the right direction but wasn't yet solving the problem - added in my solution as well. thanks for the help! – Michael Lewkowitz Nov 20 '15 at 22:44

Michael Lewkowitz · Accepted Answer · 2015-11-23T15:23:20.773

0

Because $elemMatch was returning an error (I think because reply wasn't a proper schema defined doc), I got the following to work instead.

User.findOne("_id": user._id}, function (err, doc) {
    var replies = doc.__history__.reply;
    for ( var i = 0; i < replies.length; i++ ) {
        if (replies[i].props.hasOwnProperty("tipId")) {
            // do something
            break; // stop because i only wanted the first hit
    }
}

Note: I didn't have to worry about sorting by time because __history__.reply items were already ordered by most recent first.

edited Nov 23 '15 at 15:23

answered Nov 19 '15 at 16:19

Michael Lewkowitz

11
3

Just a code note for readability, you could've done i = 0; i < replies.length; i++ and avoided creating a new variable replyCount. – Brant Nov 23 '15 at 13:06

Return a subdocument based on one of it's properties using mongoose

3 Answers3