Allows defining named scopes you wish to have cached.

cache_scopes.rb

module ActiveRecord
  module CacheScopes
    def self.included(base)
      base.extend(ClassMethods)
    end
    
    module ClassMethods
      def cache_scopes(scopes)
        class_eval "@@finder_caches ||= []"
        cattr_accessor :finder_caches
        
        scopes.each do |name, finder|
          name = name.to_s
          finder = finder.to_s
          cattr_accessor "#{name}_cache".to_sym
          class_eval <<-EOV
            @@finder_caches << :#{name}
            
            def self.#{name}
              unless (%W(production stage).include? RAILS_ENV) && ActionController::Base.perform_caching
                @@#{name}_cache = self.#{finder}
              else
                @@#{name}_cache ||= self.#{finder}
              end
            end
          EOV
        end
        
        after_save :reset_cached_finders
        after_destroy :reset_cached_finders
        class_eval <<-EOV
          def self.reset_cached_finders
            @@finder_caches.each do |finder_cache|
              self.send "\#{finder_cache}_cache=".to_sym, nil
            end
          end
          
          protected
            def reset_cached_finders
              self.class.reset_cached_finders
            end
        EOV
      end
    end
  end
end

ActiveRecord::Base.send :include, ActiveRecord::CacheScopes