Question

I have a data model as follows

• A bid is associated with the User that placed the bid
• A bid may be either an offer or a listing on a single Product
• A Product may have multiple offers and listings (separate) posted by multiple users
• A user may place offers and listings on multiple Products

Product <— Bid —> User

Given an existing p from the Product model, operations like p.offers << bid where bid is a new instance of the Bid class do not mark p as “dirty” and changes are not persisted to the database

Product class

class Product
  include Mongoid::Document
  ...
  embeds_many :offers, class_name: 'Bid'
  embeds_many :listings, class_name: 'Bid'
end

Bid class

class Bid
  include Mongoid::Document
  belongs_to :user
  belongs_to :product

  field :amount, type: Money  
  field :timestamp, type: DateTime, default: ->{ Time.now }
end

Additionally, calling bid.save! or creating a new array p.offers = Array.new [bid] do not seem to work either

Answer 1

Updated:

Your model structure should be

class Product
   include Mongoid::Document
   ...
   has_many :offers, class_name: 'Bid', :inverse_of => :offers_bid
   has_many :listings, class_name: 'Bid', :inverse_of => :listings_bid
end

class Bid
   include Mongoid::Document
   belongs_to :offers_bid, :class_name => 'Product', :inverse_of => :offers
   belongs_to :listings_bid, :class_name => 'Product', :inverse_of => :listings
   belongs_to :user

   field :amount, type: Money  
   field :timestamp, type: DateTime, default: ->{ Time.now }
end