Show sum of collections and hits count in RailsAdmin

git.diff

diff --git a/app/models/photo.rb b/app/models/photo.rb
index 3c44e48..3fc12cc 100644
--- a/app/models/photo.rb
+++ b/app/models/photo.rb
@@ -190,4 +190,8 @@ class Photo < ActiveRecord::Base
   def hide
     update_attribute(:hidden, true)
   end
+
+  def sum_of_collections_count_and_hits_count
+    collections.count + hits.count
+  end
 end
diff --git a/config/initializers/rails_admin.rb b/config/initializers/rails_admin.rb
index 732dbf6..0f3b03d 100644
--- a/config/initializers/rails_admin.rb
+++ b/config/initializers/rails_admin.rb
@@ -80,6 +80,7 @@ RailsAdmin.config do |config|
         field :score do
           column_width 8
         end
+        field :sum_of_collections_count_and_hits_count
         field :weibo_source
       end
       show do