Better way to caching.

lib/caching.rb

@@ -0,0 +1,19 @@
+module Caching
+  extend ActiveSupport::Concern
+
+  module InstanceMethods
+    def cache_key(*suffixes)
+      cache_key = case
+                    when !persisted?
+                      "#{self.class.name.downcase}-new"
+                    when timestamp = self[:updated_at]
+                      "#{self.class.name.downcase}-#{id}-#{timestamp.to_s(:number)}"
+                    else
+                      "#{self.class.name.downcase}-#{id}"
+                  end
+      cache_key += "#{suffixes.join('-')}" unless suffixes.empty?
+      cache_key
+    end
+  end # InstanceMethods
+end # Caching
+MongoMapper::Document.send(:include, Caching)