post.rb

class Post
  include DataMapper::Resource

  property :id,         Serial
  property :title,      String
  property :content,    Text
  property :tags,       String
  property :slug,       String
  property :created_at, DateTime
  property :updated_at, DateTime

  has n, :comments
#  has n, :tags

  validates_present :title, :content
  
  before :save, :set_slug

  def to_html
    red_cloth = RedCloth.new content
    red_cloth.to_html
  end

  private
  def set_slug(slug = self.title)
    self.slug = slug.downcase.gsub(/[^a-z0-9- ]/, "").gsub(/[ ]+/, " ").gsub(" ", "-")
  end
end