Populate a mongoose model with a field that isn't an id

Question

Is it possible to populate a mongoose model with a field of a reference model that isn't the _id ... e.g. a username.

so something like

var personSchema = Schema({   _id     : Number,   name    : String,   age     : Number,   stories : { type: String, field: "username", ref: 'Story' } }); 

Answer 1

This is supported since Mongoose 4.5, and is called virtuals population.

You have to define your foreign keys relationships after your schemas definitions and before creating models, like this:

// Schema definitions  BookSchema = new mongoose.Schema({         ...,         title: String,         authorId: Number,         ...     },     // schema options: Don't forget this option     // if you declare foreign keys for this schema afterwards.     {         toObject: {virtuals:true},         // use if your results might be retrieved as JSON         // see http://stackoverflow.com/q/13133911/488666         //toJSON: {virtuals:true}      });  PersonSchema = new mongoose.Schema({id: Number, ...});   // Foreign keys definitions  BookSchema.virtual('author', {   ref: 'Person',   localField: 'authorId',   foreignField: 'id',   justOne: true // for many-to-1 relationships });   // Models creation  var Book = mongoose.model('Book', BookSchema); var Person = mongoose.model('Person', PersonSchema);   // Querying  Book.find({...})     // if you use select() be sure to include the foreign key field !     .select({.... authorId ....})      // use the 'virtual population' name     .populate('author')     .exec(function(err, books) {...}) 

Answer 2

It seems they enforce to use _id, and maybe we can customize it in the future.

Here is the issue on Github https://github.com/LearnBoost/mongoose/issues/2562