Added support for counter cache column.

README.md

@@ -5,15 +5,9 @@ impressionist
 
 A lightweight plugin that logs impressions per action or manually per model
 
+I would not call this a stable plugin yet, although I have been running it in prod with no problems.  Use at your own risk ;-)
 ------------------------------------------------------------------------------------------------------------------------------
 
-NOTE: If you are upgrading from a version prior to 0.4.0, you will need to run this migration after the upgrade:
-
-https://github.com/charlotte-ruby/impressionist/blob/master/upgrade_migrations/version_0_4_0.rb
-
-If you don't run this migration you will receive this error: Unknown attribute : referrer
-
-
 What does this thing do?
 ------------------------
 Logs an impression... and I use that term loosely.  It can log page impressions (technically action impressions), but it is not limited to that.
@@ -28,7 +22,7 @@ http://www.user-agents.org/allagents.xml
 
 Which versions of Rails and Ruby is this compatible with?
 ---------------------------------------------------------
-Rails 3.0.x and Ruby 1.9.2 (also tested on REE 1.8.7) - Sorry, but you need to upgrade if you are using Rails 2.  You know you want to anyways.. all the cool kids are doing it ;-)
+Rails 3.0.4 and Ruby 1.9.2 (also tested on REE 1.8.7) - Sorry, but you need to upgrade if you are using Rails 2.  You know you want to anyways.. all the cool kids are doing it ;-)
 
 Installation
 ------------
@@ -112,6 +106,19 @@ Usage
 
 Logging impressions for authenticated users happens automatically.  If you have a current_user helper or use @current_user in your before_filter to set your authenticated user, current_user.id will be written to the user_id field in the impressions table.
 
+Adding a counter cache
+----------------------
+Impressionist makes it easy to add a `counter_cache` column to your model. The most basic configuration looks like:
+
+  is_impressionable :counter_cache => true
+
+This will automatically increment the `impressions_count` column in the included model. Note: You'll need to add that column to your model. If you'd like specific a different column name, you can:
+
+  is_impressionable :counter_cache => { :column_name => :my_column }
+
+If you'd like to include only unique impressions in your count:
+
+  is_impressionable :counter_cache => { :column_name => :my_column, :unique => true }
 
 Development Roadmap
 -------------------

app/models/impression.rb

@@ -1,3 +1,12 @@
 class Impression < ActiveRecord::Base
   belongs_to :impressionable, :polymorphic=>true
+
+  after_save :update_impressions_counter_cache
+
+  private
+
+  def update_impressions_counter_cache
+    resouce = self.impressionable_type.constantize.find(self.impressionable_id)
+    resouce.update_counter_cache if resouce.try(:cache_impression_count?)
+  end
 end

app/models/impressionist/impressionable.rb

@@ -1,7 +1,8 @@
 module Impressionist
   module Impressionable
-    def is_impressionable
+    def is_impressionable(options={})
       has_many :impressions, :as=>:impressionable
+      @counter_cache_options = options[:counter_cache] ? options[:counter_cache] : nil
       include InstanceMethods
     end
 
@@ -19,6 +20,16 @@ module Impressionist
         imps.all.size
       end
 
+      def cache_impression_count?
+        ! @counter_cache_options.nil?
+      end
+
+      def update_counter_cache
+        column_name = @counter_cache_options[:column_name] || :impressions_count
+        impression_count = @counter_cache_options[:unique] ?  impressionist_count(filter: :ip_address) : impressionist_count
+        self.class.update_attribute(column_name.to_sym, impression_count)
+      end
+
       # OLD METHODS - DEPRECATE IN V0.5
       def impression_count(start_date=nil,end_date=Time.now)
         impressionist_count({:start_date=>start_date, :end_date=>end_date, :filter=>:all})