Post.rb

class Post < ActiveRecord::Base
  # [...]
  
  named_scope :order_by        , lambda { |order| { :order => (order) } }  
  named_scope :limit           , lambda { |*lim| { :limit => (lim.first || DEFAULT_LIMIT) } }  
  named_scope :published_before, lambda { |*time|
    {:conditions => [ "published_at < ?", (time.first || Time.now) ]}}
  
  named_scope :with_comments, {:include=>:comments}
  named_scope :remove_duplications, :select => 'distinct posts.*'
 
  def self.find_recent(options = {})
    tag = options.delete(:tag)
    if tag
      published_before.limit.order_by("published_at DESC").find_tagged_with(tag, options)
    else
      published_before.limit.order_by("published_at DESC").find(:all, options)
    end
  end
 
  # more code ...
end

Post_old.rb

 class Post < ActiveRecord::Base
  # [...]
  
   def self.find_recent(options = {})
      tag = options.delete(:tag)
      options = {
        :order      => 'posts.published_at DESC',
        :conditions => ['published_at < ?', Time.zone.now],
        :limit      => DEFAULT_LIMIT
      }.merge(options)
      if tag
        find_tagged_with(tag, options)
      else
        find(:all, options)
      end
   end
end