How to add multiple ObjectIds using addToSet with Mongoose?

Question

I am trying to use mongoose addToSet to add multiple ObjectIds to a sub-doc array. I've used a similar method for adding a single subdocument, but I'm trying to figure out how to add multiple subdocuments.

Project Model

import mongoose from 'mongoose';

var Schema = mongoose.Schema;
const ProjectSchema = new Schema({
  title: {
           type: String
  },
  files: [{
            type: Schema.ObjectId,
            ref: 'File'
  }]
});

export default mongoose.model('Project', ProjectSchema);

File Model

import mongoose from 'mongoose';

var Schema = mongoose.Schema;
const FileSchema = new Schema({
  fileUrl: {
           type: String
  },
  date: {
          type: Date
  }

});

export default mongoose.model('File', FileSchema);

Controller

    Project.create({fileUrl: req.fileUrl}, (err, proj) => {
      if (err) {
        console.log(err);
        return res.status(400).send(err);
      } else {
        File.distinct('_id', {date: {"$lt": req.date }}).exec((err, files) => {
          if (err)
            return (err)
        var added = new File([files]) <-----THE PROBLEM
        proj.files.addToSet(added)
        proj.save() 
        return res.status(200).send('OK');
    })
  }
}); 

//Usually I would do something like this if I were adding one subdocument to an array: (example)

var foo = new File(file)
proj.files.addToSet(foo)
proj.save()

Answer 1

You are very close! When you're passing the added variable, you are not sending the list of values through. You are basically sending a single object of arrays.

If you'd like to perform the addToSet function, try doing a simple iteration:

files.forEach(function(f) {
    var added = new File(f)
    proj.files.addToSet(added);
    proj.save(function(err, saved){
      if (err)
        throw (err)
      return;
    })
});

You can find more examples of javascript iterators here: For-each over an array in JavaScript? There is an amazing and comprehensive list of options for you.