find_by_site_and_category.rb

  # args can be :sort_by, :order, :total, :page and :per_page
  def self.find_with_categories(site, category, args = {})
    raise "order has to be asc or desc, it was #{args[:order]}" unless %w(asc desc).include?(args[:order])

    # calculate the order by clause
    order = args[:order]
    sort_by = args[:sort_by]
    order_by = "#{connection.quote_column_name(sort_by)} #{order}"
    if sort_by == 'average_rating'
      order_by << ', rating_count desc'
    end
    if %w[username category sales_count average_rating cost].include?(sort_by)
      order_by << ', name asc'
    end

    if category && !category.parent
      #It's a root category, we can search root category field
      conditions = ["site = ? and root_category = ?", site.domain, category.path]
    elsif category
      #Use a like query
      conditions = ["site = ? and category like '#{category.path}%'", site.domain]
    else
      #Don't worry about categories at all
      conditions = ["site = ?", site.domain]
    end
    paginate :conditions => conditions,
      :order => order_by,
      :total_entries => args[:total], :page => args[:page], :per_page => args[:per_page]
  end