is_content_chunk.rb

module IsContentChunk
  def self.included(base)
    base.class_eval do
      
      named_scope :by_association, lambda{ |key| {:conditions => ['association = ?', key] } }
      
      named_scope :regional_and_or_default, lambda{ |key| {
        :include => [:region],
        :conditions => ['association = ? AND ( region_id = ? OR region_id = ? )', key, self.current_region, Region.default],
        :order => "FIELD(region_id, #{id_or_null( self.current_region )}, #{id_or_null( Region.default )})"
      } }
      
      
      def self.regional_or_default(key)
        self.current_region ? self.regional_and_or_default(key).first : self.in_default_region.by_association(key).first
      end
      
      def self.get(*args)
        args.inject([]) do |results, key|
          results << self.regional_or_default(key)
        end 
      end
      
      def self.cache_key(key,region = self.current_region)
        "#{self.name.underscore.pluralize}/#{key}-#{region.to_param}"
      end
      
      # lame but order doesn't cleanup nicely like conditions.
      def self.id_or_null(region)
        region && region.is_a?(Region) ? region.id : 'NULL'
      end
      
    end
  end 
end

is_regional.rb

module IsRegional
  def self.included(base)
    base.class_eval do
      named_scope :regional, lambda{ |*args|
        region = args && args[0].is_a?(Region) ? args[0] : self.current_region
        {
          :conditions => ['regions.id = ?', region]
        }.merge(self.is_regional_includes)
      }
      
      named_scope :in_default_region, lambda{ {
        :include => :region,
        :conditions => ['regions.id = ?', Region.default]
      }}
    
      named_scope :no_regions, lambda { self.is_regional_includes }
      
      def self.is_regional_includes
        {:include => :region}
      end
      
      def self.regional_or_default
        self.regional(self.current_region || Region.default)
      end
      
      def self.regional_or_global(region=nil)
        region.nil? ? self.no_regions : self.regional(region)
      end
      
    end
  end
end