Mongoose populate after save

Question

Mongoose populate after save

I cannot manually or automatically populate the creator field on a newly saved object ... the only way I can find is to re-query for the objects I already have which I would hate to do.

This is the setup:

var userSchema = new mongoose.Schema({   
  name: String,
});
var User = db.model('User', userSchema);

var bookSchema = new mongoose.Schema({
  _creator: { type: mongoose.Schema.Types.ObjectId, ref: 'User' },
  description: String,
});
var Book = db.model('Book', bookSchema);

This is where I am pulling my hair

var user = new User();
user.save(function(err) {
    var book = new Book({
        _creator: user,
    });
    book.save(function(err){
        console.log(book._creator); // is just an object id
        book._creator = user; // still only attaches the object id due to Mongoose magic
        console.log(book._creator); // Again: is just an object id
        // I really want book._creator to be a user without having to go back to the db ... any suggestions?
    });
});

EDIT: latest mongoose fixed this issue and added populate functionality, see the new accepted answer.

node.js
mongodb
mongoose
populate

Answer 1

You should be able to use the Model's populate function to do this: http://mongoosejs.com/docs/api.html#model_Model.populate In the save handler for book, instead of:

book._creator = user;

you'd do something like:

Book.populate(book, {path:"_creator"}, function(err, book) { ... });

Probably too late an answer to help you, but I was stuck on this recently, and it might be useful for others.

Answer 2

In case that anyone is still looking for this.

Mongoose 3.6 has introduced a lot of cool features to populate:

book.populate('_creator', function(err) {
 console.log(book._creator);
});

or:

Book.populate(book, '_creator', function(err) {
 console.log(book._creator);
});

see more at: https://github.com/LearnBoost/mongoose/wiki/3.6-Release-Notes#population

But this way you would still query for the user again.

A little trick to accomplish it without extra queries would be:

book = book.toObject();
book._creator = user;

Answer 3

Just to elaborate and give another example, as it helped me out. This might help those who want to to retrieve partially populated objects after save. The method is slightly different as well. Spent more than an hour or two looking for the correct way to do it.

  post.save(function(err) {
    if (err) {
      return res.json(500, {
        error: 'Cannot save the post'
      });
    }
    post.populate('group', 'name').populate({
      path: 'wallUser',
      select: 'name picture'
    }, function(err, doc) {
      res.json(doc);
    });
  });

Answer 4

Unfortunetly this is a long standing issue with mongoose which I believe is not solved yet:

https://github.com/LearnBoost/mongoose/issues/570

What you can do is to write you own custom getter/setter ( and set real _customer in a seperate property ) for this. For example:

var get_creator = function(val) {
    if (this.hasOwnProperty( "__creator" )) {
        return this.__creator;
    }
    return val;
};
var set_creator = function(val) {
    this.__creator = val;
    return val;
};
var bookSchema = new mongoose.Schema({
  _creator: {
     type: mongoose.Schema.Types.ObjectId,
     ref: 'User',
     get: get_creator,
     set: set_creator
  },
  description: String,
});

NOTE: I didn't test it and it might work strangely with .populate and when setting pure id.