MissingSchemaError: Schema hasn't been registered for model images - node.js

Question

I keep getting the same error that my imageSchema hasn't been registered for ImageModel when I try to populate the posts from UserModel. But I can't figure out what's the issue. I checked the image Schema file and I don't see anything wrong. Or am I missing something else?
User model
const userSchema = new mongoose.Schema(
{
name: {
type: String,
required: true
},
username: {
type: String,
required: true
},
email: {
type: String,
required: true
},
password: {
type: String,
min: 6,
max: 30
},
created: {
type: Date,
required: true,
default: Date.now
},
},
{
timestamps: true,
toJSON: {
virtuals: true
}
},
);
userSchema.virtual("posts", {
ref: "ImageModel",
foreignField: 'userId',
localField: '_id'
});
module.exports = mongoose.model('users', userSchema);
Image model
const imageSchema = new mongoose.Schema({
caption: {
type: String,
},
timeCreated: {
type: Date,
default: () => Date.now(),
},
img: {
type: String,
default: 'placeholder.jpg',
},
});
module.exports = mongoose.model("imagesPosts", imageSchema);
model routes
const UserModel = require("../models/User");
const ImageModel = require("../models/Image");
This is the code I'm working on to populate the posts from the User model, but I'm not sure if I'm doing it correctly or not.
const userId = req.user.id;
try {
const result = await UserModel.findById(userId).populate("posts");
console.log("\n\nPopulate result: " + result + "\n\n");
} catch (err) {
console.log(err);
res.status(500).send("Something went wrong, check logs");
}
**Desired output: **
{
"_id": "5e3a885ec511414a3c37a78c",
"username": "Johm",
"email": "john#head.dev",
"password": "123123",
"__v": 0,
"posts": [
{
"_id": "5e3a88e2c511414a3c37a78d",
"caption": "caption one",
"img": "1661309774553spaghetti.jpg",
"userId": "5e3a885ec511414a3c37a78c",
"created": "2020-02-05T09:20:49.754Z",
"__v": 0
},
{
"_id": "5e3a88f1c511414a3c37a78e",
"caption": "caption two",
"img": "1661309774553spaghetti.jpg",
"userId": "5e3a885ec511414a3c37a78c",
"created": "2020-02-05T09:20:49.754Z",
"__v": 0
}
],
}

Answer 1

Declare your posts field as a ref in userSchema:
const userSchema = new mongoose.Schema(
{
posts: [
{
type: mongoose.Schema.Types.ObjectId,
ref: 'imagesPosts',
},
],
...
);
You should be able to populate it with:
await UserModel.findById(userId).populate("posts").exec();