Many-to-many mapping with Mongoose

Question

I have FlashcardSchemas and PackageSchemas in my design. One flashcard can belong to different packages and a package can contain different flashcards.

Below you can see a stripped down version of my mongoose schema definitions:

// package-schema.js var Schema = mongoose.Schema,     ObjectId = Schema.ObjectId;  var PackageSchema = new Schema({     id          : ObjectId,     title       : { type: String, required: true },     flashcards  : [ FlashcardSchema ] });  var exports = module.exports = mongoose.model('Package', PackageSchema);  // flashcard-schema.js var Schema = mongoose.Schema,     ObjectId = Schema.ObjectId;  var FlashcardSchema = new Schema({     id      : ObjectId,     type        : { type: String, default: '' },     story       : { type: String, default: '' },     packages    : [ PackageSchema ] });  var exports = module.exports = mongoose.model('Flashcard', FlashcardSchema); 

As you can see from the comments above, these two schema definitions belong to separate files and reference each other.

I get an exception stating that PackageSchema is not defined, as expected. How can I map a many-to-many relation with mongoose?

Answer 1

I am new to node, mongoDB, and mongoose, but I think the proper way to do this is:

var PackageSchema = new Schema({     id: ObjectId,     title: { type: String, required: true },     flashcards: [ {type : mongoose.Schema.ObjectId, ref : 'Flashcard'} ] });  var FlashcardSchema = new Schema({     id: ObjectId,     type: { type: String, default: '' },     story: { type: String, default: '' },     packages: [ {type : mongoose.Schema.ObjectId, ref : 'Package'} ] }); 

This way, you only store the object reference and not an embedded object.

Answer 2

You are doing it the right way, however the problem is that you have to include PackageSchema in the the flashcard-schema.js, and vice-versa. Otherwise these files have no idea what you are referencing

var Schema = mongoose.Schema,     ObjectId = Schema.ObjectId;     PackageSchema = require('./path/to/package-schema.js')  var FlashcardSchema = new Schema({     id      : ObjectId,     type        : { type: String, default: '' },     story       : { type: String, default: '' },     packages    : [ PackageSchema ] });