mongoose-join.md

Hey, so this is the problem, I've two models Collection & Track. As you can tell, a collection can contain many tracks, but a track belongs to one collection

ModelCollection.ts

import mongoose, { Schema, model, SchemaType, SchemaTypes } from "mongoose";

// 1. Create an interface representing a document in MongoDB.
interface ICollection {
  userId: string;
  name: string;
  isPublic: boolean;
  isPasswordProtected: boolean;
  password?: string;
  isDownloadable: boolean;
  tracks: any[];
}

// 2. Create a Schema corresponding to the document interface.
const collectionSchema = new Schema<ICollection>({
  userId: { type: String, required: true },
  name: { type: String, required: true },
  isPublic: { type: Boolean, required: true, default: false },
  isPasswordProtected: { type: Boolean, required: true, default: false },
  password: { type: String, required: false },
  isDownloadable: { type: Boolean, required: true, default: false },
  tracks: [
    {
      type: SchemaTypes.ObjectId,
      ref: "Collection",
      required: false,
    },
  ],
});

// Add timestamps
collectionSchema.set("timestamps", true);

// 3. Create a Model.
export const ModelCollection =
  mongoose.models.Collection ||
  model<ICollection>("Collection", collectionSchema);

ModelTrack.ts

import mongoose, { Schema, model, SchemaTypes } from "mongoose";

// 1. Create an interface representing a document in MongoDB.
interface ITrack {
  collectionId: any;
  name: string;
  duration: number;
  bitrate: number;
}

// 2. Create a Schema corresponding to the document interface.
const trackSchema = new Schema<ITrack>({
  name: { type: String, required: true },
  duration: { type: Number, required: false },
  bitrate: { type: Number, required: false },
  collectionId: {
    type: SchemaTypes.ObjectId,
    ref: "Collection",
    required: false,
  },
});

// Add timestamps
trackSchema.set("timestamps", true);

// 3. Create a Model.
export const ModelTrack =
  mongoose.models.Track || model<ITrack>("Track", trackSchema);

When Im saving a track, I use track.save() as normal, and use the collectionId thinking it would link them. I'm using

  const collection = await ModelCollection.findById(
    "641987178ad2cc1cdf8a07ca",
    { password: 0 }
  )
    .populate("tracks")
    .exec();

to then retrieve a collection with it's tracks, but the array is always empty.

Any idea what I'm doing wrong? Thanks!