Undefined bson_type method for model in Rails and MongoId

I am having problems with mongoid when adding items to the embeds_many relation: undefined method bson_type for #<Discount:0x007f3c599747e8>

thanks in advance.

here is my code:

class Discount
  include Mongoid::Document
  embedded_in :discountable, polymorphic: true
end

class User
  include Mongoid::Document

  embeds_many :discounts, as: :discountable
  field :client_ids, type: Array
end

class UsersController < ApplicationController
  def review
    ...
    current_user.push discounts: like_discount
    current_user.push client_ids: params[:client_id]
    ...
  end
end

      

        
        
        
      

    

I tried with a different approach but with no success; (works for embdes_many, but not for a normal array).

class UsersController < ApplicationController
  def review
    ...
    current_user.discounts.push like_discount
    current_user.client_ids.push params[:client_id]
    ...
  end
end