Initial tagging implementation

gistfile1.rb

def Post
  attr_accessor :tag_names

  has_and_belongs_to_many :tags

  after_save :update_tags

  private
    def update_tags
      tags.clear

      if tag_names.to_s == ''
        return
      end

      tag_names.split(/,/).each do |tag_name|
        tag_name.strip!
        tag = Tag.find_or_create_by_name(tag_name)

        if !tags.exists?(tag.id)
          tags << tag
        end
      end
    end
end