Extend ActiveRecord::Base#cache_key to take an optional list of timestamp attributes of which the highest will be used.

1 files changed, 9 insertions, 1 deletions

diff --git a/activerecord/lib/active_record/integration.rb b/activerecord/lib/active_record/integration.rb
index 2589b2f3da..6449789fe4 100644
--- a/activerecord/lib/active_record/integration.rb
+++ b/activerecord/lib/active_record/integration.rb
@@ -45,10 +45,18 @@ module ActiveRecord
     #   Product.new.cache_key     # => "products/new"
     #   Product.find(5).cache_key # => "products/5" (updated_at not available)
     #   Person.find(5).cache_key  # => "people/5-20071224150000" (updated_at available)
-    def cache_key
+    # 
+    # You can also pass a list of named timestamps, and the newest in the list will be
+    # used to generate the key:
+    #
+    #   Person.find(5).cache_key(:updated_at, :last_reviewed_at)
+    def cache_key(*timestamp_names)
       case
       when new_record?
         "#{self.class.model_name.cache_key}/new"
+      when timestamp_names.any?
+        timestamps = timestamp_names.collect { |method| send(method) }.compact
+        "#{self.class.model_name.cache_key}/#{id}-#{timestamps.max.utc.to_s(:number)}"        
       when timestamp = max_updated_column_timestamp
         timestamp = timestamp.utc.to_s(cache_timestamp_format)
         "#{self.class.model_name.cache_key}/#{id}-#{timestamp}"