# The models

class VProduct
  include Mongoid::Document
  include Mongoid::Timestamps
  include Tire::Model::Search
  include Tire::Model::Callbacks

  field :name                   # name -        Bezeichnung

  belongs_to :v_group
  embeds_many :p_images

  #elastic search
  index_name 'v-products'
  def to_indexed_json
    self.to_json
  end
end

class SubCalculation
  include Mongoid::Document
  # Timestamps sind im Objekt Berechnung

  ###############    RELATIONS   #################
  embedded_in :calculation
  embeds_many :left_products, class_name: "VProduct"
  embeds_many :right_products, class_name: "VProduct"
end

# The Problem

a = Calculation.new
a.build_subcalculation
a.subcalculation.left_products << [VProduct.first]
a.subcalculation.left_products << [VProduct.last]
a.subcalculation.left_products.count
=> 2
a.save
=>true
# works fine :-) sweet
# BUT

a.subcalculation.left_products << [VProduct.where(vid: 45).first]
=>true
a.subcalculation.left_products.count
=> 3
a.changed?
=> false
a.subcalculation.changed?
=>false
a.save
=>true

# But it doenst save the new product. 
# so i guess the dirty/change-tracking has a bug.

# best regards
# im using mongoid 2.4.6 and rails 3.1.3