How to write a Mongoose query for items whose IDs are not in an array

Question

I have two models: Event and People.

schemas.event = new mongoose.Schema({
    eventId: Number,
    name: {type: String},
    size: Number,
    location: {type: String},
    date: {type: Date},     
    people: [{type: mongoose.Schema.Types.ObjectId, ref: models.Person}],
    note: {type: String}
});

and People

schemas.person = new mongoose.Schema({
    firstname: {type: String},
    lastname: {type: String},
    age: Number,
    email: {type: String},
    gender: {type: String}
});

Given a certain event, I want to do a Query using Mongoose, to find all the people not already registered for this event.

Something like

models.Person.find({not in event.people});

The tricky thing for me is, that event.people is not an array of IDs, but rather it is an array of Objects that look like

[
        {
            "$oid": "558ced061d35bd072e7b5825"
        },
        {
            "$oid": "558ced061d35bd072e7b58a0"
        },
        {
            "$oid": "558ced061d35bd072e7b58c6"
        }
    ],

Is there any way to simply make this query?

chridam · Accepted Answer · 2015-06-29 17:53:29Z

3

Firstly, you need to create an array of the ObjectId's by using the native JavaScript method map() which creates a new array with the results of calling a provided function on every element in this array:

var mongoose = require("mongoose");
var arr = event.people.map(function(item){ return mongoose.Types.ObjectId(item["$oid"])});

You can then query the collection using that as the $nin operator expression:

models.Person.find({"_id": { "$nin": arr}}).exec(callback);

edited Jun 29, 2015 at 17:53

answered Jun 29, 2015 at 16:48

chridam

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3 Comments

CodyBugstein Over a year ago

mongoose.Types.ObjectId(item["$oid"]) seems to be returning a brand new oid which is not what I want. I think I will just return item["$oid"] ... edit: but it returns null....

chridam Over a year ago

What about if you map it directly without casting to ObjectId event.people.map(function(item){ return item["$oid"]});?

CodyBugstein Over a year ago

Yes, it worked now. I made a mistake in that I was populating them before... anyway it works now! Thanks a lot

GPicazo · Accepted Answer · 2015-06-29 16:36:44Z

0

Look into the following operators:

$not - http://docs.mongodb.org/manual/reference/operator/query/not/
$in - http://docs.mongodb.org/manual/reference/operator/query/in/
$nin - http://docs.mongodb.org/manual/reference/operator/query/nin/

answered Jun 29, 2015 at 16:36

GPicazo

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1 Comment

Jason Cust Over a year ago

Just as an FYI: your answer is more of a comment than an answer.

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