Mongoose populate within an object?

Question

I'm not sure how to populate the sample schema below or if it is even possible. Can a reference be within an object like below? If you can, how would you populate it? E.g. .populate('map_data.location');?

var sampleSchema = new Schema({
  name: String,
  map_data: [{
    location: {type: Schema.Types.ObjectId, ref: 'location'},
    count: Number
  }]
});

Or will I have to have two separate arrays for location and count like so:

// Locations and counts should act as one object. They should
// Be synced together perfectly.  E.g. locations[i] correlates to counts[i]
locations: [{ type: Schema.Types.ObjectId, ref: 'location'}],
counts: [Number]

I feel like the first solution would be the best, but I'm not entirely sure how to get it working within Mongoose.

Thank you very much for any help!

score 30 · Accepted Answer · answered Jan 30 '13 at 00:41

The first solution is possible.

Mongoose currently has limitations (see this ticket here) populating multiple levels of embedded documents, however is very good at understanding nested paths within a single document - what you're after in this case.

Example syntax would be:

YourSchema.find().populate('map_data.location').exec(...)

Other features, such as specifying getters / setters on paths, orderBy and where clauses, etc. also accept a nested paths, like this example from the docs:

personSchema.virtual('name.full').get(function () {
  return this.name.first + ' ' + this.name.last;
});

Internally Mongoose splits the string at the dots and sorts everything out for you.

As far as the second point goes: Do you have a top element? If so, give everything a top_id and a parent_id. Or descendents array and a children array. Then, take everything from top, and sort out inheritance on client side. — dansch, Nov 17 '13 at 03:08

score 18 · Answer 2 · answered Aug 17 '16 at 20:41

18

First option is ok, but if someone would have problems with that query map_data.location - Mongoose returns empty array instead of object - I found that this will work:

.populate({
     path: 'map_data.location',
     model: 'Location'
})

answered Aug 17 '16 at 20:41

kkochanski

2,178
23
28

According to the [**documentation**](https://mongoosejs.com/docs/populate.html#cross-db-populate), it seems that specifying the `model` key is only useful if you need to populate across MongoDB databases or MongoDB instances. – Chunky Chunk Aug 19 '19 at 02:16

score 4 · Answer 3 · edited Oct 30 '20 at 09:53

4

   YourSchema.find()
       .populate({
            path: 'map_data',
            populate: {
                path: 'location' 
            }
    }).exec(...)

The above statement will populate array of map_data and also the location object of each map_data.

hope this helps someone.

edited Oct 30 '20 at 09:53

Akash Kumar Verma

3,185
2
16
32

answered May 23 '18 at 22:26

Otis-iDev

101
1
4

Rodolfo Merlo Ali · Answer 4 · 2020-06-16T19:52:22.910

2

i think you will need this:

if you schema is this:

var sampleSchema = new Schema({
name: String,
map_data: [{
location: {type: Schema.Types.ObjectId, ref: 'location'},
count: Number
}]
});

you monggosse query have to be:

const responseMap=await YourSchema.find()
.populate(
path: 'map_data._id',
model: 'location'
select:['nameLocation','geoPoints','count'],
).exec();
console.log(responseMap);

but you count variable have to be in location schema, and map_data have to containt only id location.

edited Jun 16 '20 at 19:52

answered May 15 '20 at 15:41

Rodolfo Merlo Ali

141
1
8

1

Welcome to StackOverflow. We usually don't recommend sending regards, thanks, or any other tagline in order to keep the content of the answer clear & concise and to adhere to the technical writing guidelines. – Bassem May 15 '20 at 22:05

score 1 · Answer 5 · answered Mar 16 '22 at 06:20

If someone couldn't solve his/her problem I got a solution It works for me.

My Schema:

const categorySchema = new Schema(
{
    name: {
        type: String,
        unique: true
    },
    products: [{
        type: Schema.Types.ObjectId,
        ref: 'Product'
    }]
})

And then to get a category with an specific name and with their products:

.get('/:name', async (req, res) => {
const { name } = req.params;
    
    const responseMap = await Category.find({name})
            .populate({
                path: 'products',
                model: 'Product',
            })
            .exec();

    res.send(responseMap);})

score 0 · Answer 6 · answered Jan 30 '13 at 00:25

0

The first option is the best. "count" is part of object "map_data".

answered Jan 30 '13 at 00:25

Daniel Martin Jimenez

9
2

Mongoose populate within an object?

6 Answers6

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