CODEWITHSUNDEEP
node.jsmongodbmongoose
Laurence
Laurence

Reputation: 879

mongooseJS can not populate order with items

I'm trying to get mongoose populate to work.

I have two models one for orders and the other for the order items.

I'm doing this purely to understand populate.

I did have two files for this but I have now got everything in one file called main.js

main.js creates the 3 items in items model.

I then try to populate the order model with the 3 items.

Output for the query now gives the correct populated result.

That is to say the output from the line

console.log(JSON.stringify(orders, null, "\t");

is now:

[ { "_id": "55d32e4594db780b1bbb4372", "__v": 0, "lines": [ { "price": 2.4, "quantity": 5, "_id": "55d32e4594db780b1bbb436f", "__v": 0 }, { "price": 3.7, "quantity": 7, "_id": "55d32e4594db780b1bbb4370", "__v": 0 }, { "price": 1.2, "quantity": 3, "_id": "55d32e4594db780b1bbb4371", "__v": 0 } ] } ]

The database however is not populating.

Below is the main.js file

var mongoose = require('mongoose');

mongoose.connect('mongodb://localhost:27017/mydb');

var Schema = mongoose.Schema;

var OrderSchema = new Schema({
  lines: [{type: mongoose.Schema.Types.ObjectId, ref: 'Item'}]
});

var ItemSchema = new Schema({
  price: Number,
  quantity: Number
});

var Order = mongoose.model('Order', OrderSchema);
var Item = mongoose.model('Item', ItemSchema);

var itemArray = [
  {price: 2.4, quantity: 5},
  {price: 3.7, quantity: 7},
  {price: 1.2, quantity: 3}
];

Item.create(itemArray, function(err) {
  if (err) {
    console.log('Error creating items: ', err);
  }

  var order = new Order();
    Item.find({}, {_id: 1}, function(err, result) {
        result.forEach(function(obj) {
                order.lines.push(obj._id);
        });
    }).exec().then(function() {
        order.save(function(err) {
            if (!err) {
                Order.find({})
                    .populate('lines')
                    .exec(function(err, orders) {
                        console.log(JSON.stringify(orders, null, "\t")); // output is populated the database is still not populating.

                    });
            }
        });
}    );
});

Upvotes: 0

Views: 355

Answers (1)

Jason Cust
Jason Cust

Reputation: 10899

It appears there is some confusion for what the populate method is for. Essentially populate is mongoose's version of a "join". It allows a query (or a document) to automatically retrieve and "join" any associated documents and returns the modified document(s). Under the hood for every referenced value in a document that is to be populated, the populate method will execute a separate query to fetch those associated documents (generally this is by ID but can be a custom query) and then in memory it will replace the references with the retrieved documents.

It does not alter the documents in the collection at all as this is purely a fetch operation.

Upvotes: 0

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