Mongoose Nested Populate Not Working

Question

So I am currently extremely confused when it comes to mongoose populating.

My data structure is as follows: User has an array of Clients, a Client has an array of loans. I am using User.find and populating the client, no problem. But then how do I populate the loans that is inside of the client? I have tried this:

Basically, the goal is to pass in an array of Clients, each client will contain a loan. But for now, I want that loan object to be empty. The Client is being populated correctly, however, the Loan reference is being passed as undefined.

app.get("/loans", IsLoggedIn, function(req, res) {
  User.findById(req.user._id).populate({path: "clients", populate: { path: "loans", model: "loan"}}).exec(function(err, user){
    if(err){
      console.log(err);
    } else{
        var amountRepaid = calcRepaid(user.clients.loans);
        console.log(user.clients.loans);
        res.render("index", {clients: user.clients, amountRepaid: amountRepaid});
    }
  });

However it doesn't seem to work, my models are listed below and any help is appreciated!

models:

Client:

var mongoose = require("mongoose");
var clientSchema = mongoose.Schema({
  loans: [{
    type: mongoose.Schema.Types.ObjectId,
    ref: "loan"
  }],
  emailAdderess: String,
  firstname: String,
  lastname: String,
  contactNumber: String ,
  dateCreated: {type: Date, default: Date.now},
  gender: String,
})

module.exports = mongoose.model("Client", clientSchema);

User:

const mongoose = require("mongoose");
const passportLocalMongoose = require("passport-local-mongoose");
var UserSchema = mongoose.Schema({
  username: String,
  password: String,
  firstname: String,
  lastname: String,
  clients: [{
    type: mongoose.Schema.Types.ObjectId,
    ref: "Client"
  }]
});
UserSchema.plugin(passportLocalMongoose);

module.exports = mongoose.model("User", UserSchema);

Loan:

var mongoose = require("mongoose");

var LoanSchema = mongoose.Schema({
  firstName: String,
  lastName: String,
  email: String,
  contactNumber: Number,
  amountBorrowed: Number,
  length: String,
  address: String,
  dateDue: Date,
  gender: String,
  date: { type: Date, default: Date.now },
  amountRepaid: { type: Number, default: 0},
  loanRepaid: {type: Boolean, default: false}

})

module.exports = mongoose.model("loan", LoanSchema);

When asking questions here, please to not use external links or images of of code and include the relevant code in the question. Also it helps to make the example reproducible, and in this case that would mean including a "sub-set" of the relevant data which should produce the expected result. See How to create a Minimal, Complete, and Verifiable example. Your likely cause here is that the references to not actually match between models. This is what you should look at, and if you cannot resolve then provide enough data to return at least one result. — Neil Lunn
– Neil Lunn, Commented Aug 8, 2017 at 0:58
@NeilLunn Sorry posted this just before I went to bed after trying to fix it for hours, my bad. The reason I didn't include a sub-set of data is because I'm not using one. I want to pass in an empty array at the beginning and the User would later add to it. I'll add that to the question. I don't understand what you mean when you say the references do not match between models? Could you possibly expand a bit? Thanks. — Cathal
– Cathal, Commented Aug 8, 2017 at 13:00
@Cathal did you ever figure this out? I'm having the exact same issue. — D. Reagan
– D. Reagan, Commented Jul 20, 2018 at 21:13

Helder De Baere · Accepted Answer · 2017-08-08 13:10:42Z

3

Try this:

.populate({
    path: 'clients',
    populate: {
        path: 'clients.loans'
    }
})

answered Aug 8, 2017 at 13:10

Helder De Baere

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5 Comments

Cathal Over a year ago

This seems to make things work as clients isn't being populated, which means loans isn't populated either

Helder De Baere Over a year ago

Hmmn weird, I used to do it this way and it worked for me... try removing the model part in the nested populate? I don't think it's necessary.

Cathal Over a year ago

I have genuinely tried about 8 different syntax for the populate method and none seem to work and I am not sure why. Yeah I tried removing the model and it didn't work either, have tried having the second populate as "clients.loans" and just "Loans" and that didn't work either.

Helder De Baere Over a year ago

Oh I see the problem. You're trying to access 'user.clients.loans' but user.clients is an array, so the correct way to do it would be 'user.clients[i].loans'

Cathal Over a year ago

Okay sounds promising! I'm going to try this and create some sample data and see if it works, thanks! I'll come back and let you know

D. Rattansingh · Accepted Answer · 2023-07-23 01:03:02Z

0

Try this:

const User=require('../models/user') <-- change path to your user schema
const Loan=require('../models/loan') <-- change path to your loan schema

User.findById(req.user._id).populate({path: 'clients', model: Loan})

edited Jul 23, 2023 at 1:03

answered Jul 23, 2023 at 0:34

D. Rattansingh

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