updated readme

app/models/topic.rb

@@ -0,0 +1,37 @@
+class Topic < ActiveRecord::Base
+  
+  # Associations
+  has_many :posts, :dependent => :destroy
+  belongs_to :forum, :counter_cache => true
+  belongs_to :user, :class_name => "User", :counter_cache => true
+  
+  # Accessors
+  attr_accessor :body
+  attr_accessible :title, :body, :sticky, :locked
+  
+  # Validations
+  validates :title,   :presence => true
+  validates :body,    :presence => true, :on => :create
+  validates :posts,   :presence => true, :allow_nil => false, :on => :update
+  validates :user,    :presence => true
+  
+  # Scopes
+  default_scope :order => 'sticky DESC, updated_at DESC'
+  
+  # Callbacks
+  after_create :create_initial_post
+  
+  # Methods
+  def hit!
+    self.class.increment_counter :hits, id
+  end
+  
+  private
+    def create_initial_post
+      returning self.posts.build(:body => self.body) do |post|
+        post.forum = self.forum
+        post.user = self.user
+        post.save
+      end
+    end
+end