query and populate a DBRef in a subDocument

[Jonas Garbuio]

Hi.

I have a symfony App using Doctrine ODM and I'd like to make a little node script to do some changes in DB.

With this, I have a CHapter Document with this architecture:

{
...
    pages: [
        {
             ...
             image : DBRef to files.files
        }
    ]
}

And in node with mongoose I'd like to populate pages.image when I findById a chapter but I can't get it to work.

Here are my schemas : 

//instantiate mongoose-gridfs
var gridfs = require('mongoose-gridfs')({
    collection:'files',
    mongooseConnection: mongoose.connection
});


//Files = gridfs.model;
var FilesSchema = gridfs.schema;


FilesSchema.add({
    _id: Schema.Types.ObjectId,
    name: String,
    mime: String,
    filename: String,
    type: String
});


Files = mongoose.model('Files', FilesSchema);


var pageSchema = Schema({
    order: Number,
    image: { type: Schema.Types.ObjectId, ref: 'Files' },
    scrambled: Boolean
});


var ChapterSchema = Schema({
    _id: Schema.Types.ObjectId,
    pages: [pageSchema]
});


var Chapter = mongoose.model('Chapter', ChapterSchema, "Chapter");

and my find

Chapter.findById(chapterId)
        .populate('pages.image')
        exec(...

and then I have this error : { CastError: Cast to ObjectId failed for value "DBRef ...

complete message here : https://pastebin.com/8n54Dhzt

I thought about creating a model Image with the DBRef property ($id, $db, $ref) and use the ObjetID Types on the $id property but I'm not sure it's a good idea.