Empty array being returned by Mongoose after calling the populate() function

Question

Empty array being returned by Mongoose after calling the populate() function

I've been struggling for the past 3-4 hours, banging my head against the wall and scouring countless articles here on StackOverflow, but I just can't seem to get my response to populate an array correctly. I'm working with Express.js, Typescript, MongoDB, and mongoose. The issue arises when I receive a response containing all the orders; my orderedlines array remains empty despite confirming that the ids are present in MongoDB atlas. Here is the actual response:

[
  {
    "orderedlines": [],
    "_id": "6251c61f7385c349f88fe95a",
    "userId": {
      "favourites": [
        "623b39e684b9baf1109053f8",
        "623b3afada0e7828602c78df",
        "623b3b49da0e7828602c78e7",
        "623b39ba84b9baf1109053f7",
        "623b3b59da0e7828602c78e9"
      ],
      "_id": "62326179b9c85d3fc833d686",
      "orders": [],
      "email": "<a href="/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="c6b2a3b5b2a5aea399a3aba7afaaa5aea386a1aba7afaae8a5a9ab">[email protected]</a>",
      "username": "stef1222",
      "password": "$2b$10$3e5Y/IoyrcJHH3ud6Mn/I.8PfBm2JrEKHwYRd8cQwUaAdz.YkKSMa",
      "firstName": "Stefan",
      "lastName": "Georgiev",
      "image": "https://res.cloudinary.com/dtggdx3hc/image/upload/v1648046254/deqr4chfysogoppafdug.png",
      "isAdmin": false,
      "hasWriteAccess": false,
      "__v": 0
    },
    "totalPrice": 121.99,
    "__v": 0
  }
]

Despite successfully populating my userId with all its properties, the orderedlines field fails to populate and is returned as an empty array. Removing .populate() results in an array of objects with ids.

The problem likely lies in my findOrdersForUserId function in orderServices:

const findOrdersForUserId = async (
  userId: string
): Promise<OrderDocument[]> => {
  const ordersToReturn = await Order.find({ userId: userId })
    .sort({ _id: 1 })
    .populate('userId')
    .populate({path:'orderedlines', model:OrderLine})
  return ordersToReturn
}

Here is my Order model:

import mongoose, { Document } from 'mongoose'

export type OrderLine = {
  orderlineId: string
}

export type OrderDocument = Document & {
  userId: string
  orderedlines: OrderLine[]
  totalPrice: number
}

const orderSchema = new mongoose.Schema({
  userId: { type: mongoose.Schema.Types.ObjectId, ref: 'User', required: true },
  totalPrice: Number,
  orderedlines: [
    {
      type: mongoose.Schema.Types.ObjectId,
      ref: 'OrderLine',
    },
  ],
})

export default mongoose.model<OrderDocument>('Order', orderSchema, 'orders')

My OrderLine model:

import mongoose, { Document } from 'mongoose'

export type OrderLineDocument = Document & {
  productId: string
  userId: string
  quantity: number
  price: number
}

const orderLineSchema = new mongoose.Schema({
  quantity: { type: Number, default: 1 },
  price: Number,
  productId: {
    type: mongoose.Schema.Types.ObjectId,
    ref: 'Product',
    required: true,
  },
  userId: {
    type: mongoose.Schema.Types.ObjectId,
    ref: 'User',
    required: true,
  },
})

export default mongoose.model<OrderLineDocument>('OrderLine', orderLineSchema, 'orderlines')

Mongoose version used: <a href="/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="e4898b8a838b8b9781a4d1cad5d7Cad5D4">[email protected]</a>
Node version: v16.13.0
Mongo Shell version: v5.0.6
Express version: <a href="/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="46233e363423353506726877716877">[email protected]</a>

I've attempted various articles to resolve the issue without success:

Mongoose populate returning empty array
Mongoose populate() returning empty array
Mongoose populate() returns empty array with no errors
Mongoose Populate not working with Array of ObjectIds
Populate method not populating my comment array
Mongoose populate does not populate array
Mongoose populate not populating an array and always returns an empty array

Edit: All the code is a part of a fork from a repo that is set to private. I am not sure how can I share access/link to the fork for a better preview of the code. Please enlighten me if you would like to see something else or a more specific part of the code.

typescript mongodb express mongoose mongoose-populate

Answer 1

Answer №1

Your implementation of the `OrderLine` type looks like this:

export type OrderLine = {
  orderlineId: string
}

Subsequently, you declared `orderedlines` as an array of `OrderLine`:

orderedlines: OrderLine[]

In your scenario, `orderedlines` should actually be an array of `ObjectId`, not objects with a nested property of `orderlineId`. TypeScript may perform some kind of internal casting when defining a model.

Consider modifying `orderedlines` to be an array of `ObjectId` and then retesting your code?

Answer 2

Your implementation of the `OrderLine` type looks like this:

export type OrderLine = {
  orderlineId: string
}

Subsequently, you declared `orderedlines` as an array of `OrderLine`:

orderedlines: OrderLine[]

In your scenario, `orderedlines` should actually be an array of `ObjectId`, not objects with a nested property of `orderlineId`. TypeScript may perform some kind of internal casting when defining a model.

Consider modifying `orderedlines` to be an array of `ObjectId` and then retesting your code?

Answer 3

Answer №2

Sharing my insights by answering my own question, as I encountered significant challenges and aim to assist future readers facing the same issue. One crucial aspect to consider is specifying a collection name in your model creation process. To define a collection name, include a third argument in your model creation like this:

export default mongoose.model<OrderLineDocument>('OrderLine',orderLineSchema,'orderLines')

Prior to adding the third argument, Mongoose automatically generated a collection name using a lower-cased pluralized version of the model name - 'orderlines'. However, when attempting to populate my response data, I referenced 'orderLines' with a capital L. Therefore, it's essential to always specify your collection name or verify the collection name in your MongoDB Shell/ MongoDB Atlas.

Another important point is ensuring that the _ids of the array/object you intend to populate are indeed correct _ids existing in your database. Using non-existent or incorrect _ids could result in an empty array being returned or trigger errors.

For instance, I encountered errors initially due to adding the following, but those _ids did not exist (I had previously deleted them) in my orderLines collection (note: you can add non-existing _ids if they follow the correct _id structure).

POST http://localhost:5000/api/v1/orders/62326179b9c85d3fc833d686
Content-Type: application/json

{
  "orderedlines":[
      {"_id": "6251be4d4186c34788e4f034"},
      {"_id": "6251be494186c34788e4f030"}
  ],
  "totalPrice":"121.99"
}

In TypeScript, there are three effective approaches to handling this situation:

Defining custom types

export type OrderLine = {
  _id: string
}

export type OrderDocument = Document & {
  userId: string
  orderedlines: OrderLine[],
  totalPrice: number
}

Indicating an array of strings

export type OrderDocument = Document & {
  userId: string
  orderedlines: string[],
  totalPrice: number
}

Using Array of ObjectIds

export type OrderDocument = Document & {
  userId: string
  orderedlines: mongoose.Schema.Types.ObjectId[]
  totalPrice: number
}

After considering these aspects, the approach that ultimately worked for me was:

const findOrdersForUserId = async (
  userId: string
): Promise<OrderDocument[]> => {
  const ordersToReturn = await Order.find({ userId: userId })
    .sort({ _id: 1 })
    .populate('userId')
    .populate({
      path: 'orderedlines',
      populate: { path: 'productId', model: 'Product' },
    })
  return ordersToReturn
}

The provided snippet showcases how both orderedline, productId, and userId are correctly populated in the response:

{
        "quantity": 4, //part of a single orderedline object
        "_id": "6251be494186c34788e4f030", //part of a single orderedline object
        "productId": { // beginning of populated productId
          "_id": "623b3b24da0e7828602c78e3",
          "name": "AMY SS14R - TRICKSTER",
          "image": "https://res.cloudinary.com/dtggdx3hc/image/upload/v1648048425/amy-deluxe-stick-steel-r-ss09r10_1000x1000_bfngtl.jpg",
          "price": 1299,
          "__v": 0
        }, // end of populated productId
        "price": 2.99, //part of a single orderedline object
        "__v": 0 //part of a single orderedline object
      }
    ], // end of the orderedline array of objects
    "_id": "6252bfa8dd00081d7c273e4d", // _id of the order
    "userId": { //beginning of populated userId
      "favourites": [
        "623b39e684b9baf1109053f8",
        "623b3afada0e7828602c78df",
        "623b3b49da0e7828602c78e7",
        "623b39ba84b9baf1109053f7",
        "623b3b59da0e7828602c78e9"
      ],

Answer 4

Sharing my insights by answering my own question, as I encountered significant challenges and aim to assist future readers facing the same issue. One crucial aspect to consider is specifying a collection name in your model creation process. To define a collection name, include a third argument in your model creation like this:

export default mongoose.model<OrderLineDocument>('OrderLine',orderLineSchema,'orderLines')

Prior to adding the third argument, Mongoose automatically generated a collection name using a lower-cased pluralized version of the model name - 'orderlines'. However, when attempting to populate my response data, I referenced 'orderLines' with a capital L. Therefore, it's essential to always specify your collection name or verify the collection name in your MongoDB Shell/ MongoDB Atlas.

Another important point is ensuring that the _ids of the array/object you intend to populate are indeed correct _ids existing in your database. Using non-existent or incorrect _ids could result in an empty array being returned or trigger errors.

For instance, I encountered errors initially due to adding the following, but those _ids did not exist (I had previously deleted them) in my orderLines collection (note: you can add non-existing _ids if they follow the correct _id structure).

POST http://localhost:5000/api/v1/orders/62326179b9c85d3fc833d686
Content-Type: application/json

{
  "orderedlines":[
      {"_id": "6251be4d4186c34788e4f034"},
      {"_id": "6251be494186c34788e4f030"}
  ],
  "totalPrice":"121.99"
}

In TypeScript, there are three effective approaches to handling this situation:

Defining custom types

export type OrderLine = {
  _id: string
}

export type OrderDocument = Document & {
  userId: string
  orderedlines: OrderLine[],
  totalPrice: number
}

Indicating an array of strings

export type OrderDocument = Document & {
  userId: string
  orderedlines: string[],
  totalPrice: number
}

Using Array of ObjectIds

export type OrderDocument = Document & {
  userId: string
  orderedlines: mongoose.Schema.Types.ObjectId[]
  totalPrice: number
}

After considering these aspects, the approach that ultimately worked for me was:

const findOrdersForUserId = async (
  userId: string
): Promise<OrderDocument[]> => {
  const ordersToReturn = await Order.find({ userId: userId })
    .sort({ _id: 1 })
    .populate('userId')
    .populate({
      path: 'orderedlines',
      populate: { path: 'productId', model: 'Product' },
    })
  return ordersToReturn
}

The provided snippet showcases how both orderedline, productId, and userId are correctly populated in the response:

{
        "quantity": 4, //part of a single orderedline object
        "_id": "6251be494186c34788e4f030", //part of a single orderedline object
        "productId": { // beginning of populated productId
          "_id": "623b3b24da0e7828602c78e3",
          "name": "AMY SS14R - TRICKSTER",
          "image": "https://res.cloudinary.com/dtggdx3hc/image/upload/v1648048425/amy-deluxe-stick-steel-r-ss09r10_1000x1000_bfngtl.jpg",
          "price": 1299,
          "__v": 0
        }, // end of populated productId
        "price": 2.99, //part of a single orderedline object
        "__v": 0 //part of a single orderedline object
      }
    ], // end of the orderedline array of objects
    "_id": "6252bfa8dd00081d7c273e4d", // _id of the order
    "userId": { //beginning of populated userId
      "favourites": [
        "623b39e684b9baf1109053f8",
        "623b3afada0e7828602c78df",
        "623b3b49da0e7828602c78e7",
        "623b39ba84b9baf1109053f7",
        "623b3b59da0e7828602c78e9"
      ],

Answer 5

Answer №3

My experience mirrored yours. The problem I encountered was that, after I "Post"/generate the object, I followed the typical

const orderLine = new OrderLine({object})

but failed to

await orderLine.save()

Remember to review your post before finalizing it.

Answer 6

My experience mirrored yours. The problem I encountered was that, after I "Post"/generate the object, I followed the typical

const orderLine = new OrderLine({object})

but failed to

await orderLine.save()

Remember to review your post before finalizing it.

Empty array being returned by Mongoose after calling the populate() function

Answer №1

Answer №2

Answer №3

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