#167 More on Virtual Attributes

script/generate model tag name:string
script/generate model tagging article_id:integer tag_id:integer
rake db:migrate

class Tagging < ActiveRecord::Base
  belongs_to :article
  belongs_to :tag
end

class Tag < ActiveRecord::Base
  has_many :taggings, :dependent => :destroy
  has_many :articles, :through => :taggings
end

class Article < ActiveRecord::Base
  has_many :comments, :dependent => :destroy
  has_many :taggings, :dependent => :destroy
  has_many :tags, :through => :taggings
  validates_presence_of :name, :content
  attr_writer :tag_names
  after_save :assign_tags
  
  def tag_names
    @tag_names || tags.map(&:name).join(' ')
  end
  
  private
  
  def assign_tags
    if @tag_names
      self.tags = @tag_names.split(/\s+/).map do |name|
        Tag.find_or_create_by_name(name)
      end
    end
  end
end

<p>
  <%= f.label :tag_names %><br />
  <%= f.text_field :tag_names %>
</p>