gistfile1.rb

class Post
  include Mongoid::Document
  include Mongoid::Paranoia
  include Mongoid::Timestamps
  
  field :title, :type => String
  
  attr_accessor :tags_string

  accepts_nested_attributes_for :answers

  belongs_to :user
  has_many :answers, :allow_destroy => true

  has_and_belongs_to_many :tags

  after_save :save_answers, :link_tags
  

  def save_answers
    answers.each do |a|
      a.save
    end
  end
  
  def link_tags
    return if self.tags_string.nil?
    self.update_attribute :tag_ids, tags_string.split(',').collect{|t| Tag.find_or_create_by(:t => t.downcase.strip).id}
    self.reload
  end

end