mongoose find a document by reference property

Question

I have a first model Person:

var personSchema    = new Schema({
    firstname: String,
    name: String
});
module.exports = mongoose.model('Person', personSchema);

And a second model Couple:

var coupleSchema    = new Schema({
    person1: [{ type: Schema.Types.ObjectId, ref: 'Person' }],
    person2: [{ type: Schema.Types.ObjectId, ref: 'Person' }]
});
module.exports = mongoose.model('Couple', coupleSchema);

I find a couple with a person ObjectId:

    Couple.find({
        'person1': req.params.objectid
    })
    .populate({
        path: 'person1 person2'
    })
    .exec(function (err, couple) {
        if (err)
            res.send(err);
        res.json(couple)
    });

But I would like to find a couple by giving a firstname and not an ObjectId of a Person, something like that:

    Couple.find({
        'person1.firstname': "Bob"
    })
    .populate({
        path: 'person1 person2'
    })
    .exec(function (err, couple) {
        if (err)
            res.send(err);
        res.json(couple)
    });

But it is always empty...

Anyway to solve this?

Thank you for any feedback.

EDIT

I just implemented the answer:

Let's see my Couple model now:

var Person      = require('mongoose').model('Person');
var coupleSchema    = new Schema({
    person1 : [{ type: Schema.Types.ObjectId, ref: 'Person' }],
    person2 : [{ type: Schema.Types.ObjectId, ref: 'Person' }]
});

coupleSchema.statics.findByUsername = function (username, callback) {
  var query = this.findOne()

  Person.findOne({'firstname': username}, function (error, person) {
    query.where(
      {person1: person._id}
    ).exec(callback);
  })
  return query
}

module.exports = mongoose.model('Couple', coupleSchema);

With this usage:

Couple.findByUsername(req.params.username, function (err, couple) {
        if(err)
            res.send(err);
        res.json(couple);
    });

That works! Thank you for your answer and edits.

Answer 1

In your couple model, person1 is an ObjectID (I know you know it), so it has no obviously no property .firstname .

Actually the best way to achieve this, is to find the user by it's first name, and then query the couple, with the id of the user.

This method could/should stand in the couple model as a static method (simplified code sample):

couple.statics.findByPersonFirstname = function (firstname, callback) {
  var query = this.findOne()
 
  Person.findOne({firstname: firstname}, function (error, person) {
    query.where($or: [
      {person1: person._id},
      {person1: person._id}
    ]).exec(callback);
  })

  return query
}

Just like this exemple .

EDIT: Also note that the ref must be the _id (so you couldn't store with the first name, that would be a bad idea anyway).

Considering your edit:

Person._id is maybe a String and the reference is an ObjectId , if so, try:

{person1: mongoose.Types.ObjectId(Person._id)}

Also, your variable is person and not Person . Try to log person to see if you get something.

Finally, my code sample is really simple, don't forget to handle errors and all (see the link I gave you above, which is complete).