Workaround for mongo-id-associations

workaround_mongo_associations.rb

class Author 
  include Mongoid::Document
  include Mongoid::Timestamps
 ...
  references_and_referenced_in_many :institutes

  after_save :update_institutes  #WORKAROUND 
...
  private
...
  
  def update_institutes
    for institute in self.institutes
      institute.author_ids ||= []
      institute.authors << self unless institute.authors.include?(self)
      institute.save
    end
  end
end