Mongoose: deep population (populate a populated field)

Question

I have Category model:

Category:
    ...
    articles: [{type:ObjectId, ref:\'Article\'}]

Article model contains ref to

Answer 1

This concept is deep Population. Here Calendar,Subscription,User,Apartment are mongoose ODM models in different levels

Calendar.find({}).populate({
      path: 'subscription_id',model: 'Subscription',
         populate: {path: 'user_id',model: 'User',
           populate: {path: 'apartment_id',model: 'Apartment',
              populate: {path: 'caterer_nonveg_id',
                          model: 'Caterer'}}}}).exec(function(err,data){ 
                          if(!err){
                             console.log('data all',data)
                           }
                           else{
                             console.log('err err err',err)
                            }
                   });