Merge pull request #451 from seuros/dgilperez-counter_cache

[Fix] counter_cache, Check for #390 to prevent application breakage.

lib/acts_as_taggable_on/tagging.rb

@@ -9,42 +9,36 @@ class Tagging < ::ActiveRecord::Base #:nodoc:
                     :tagger,
                     :tagger_type,
                     :tagger_id if defined?(ActiveModel::MassAssignmentSecurity)
-
     belongs_to :tag, :class_name => 'ActsAsTaggableOn::Tag'
     belongs_to :taggable, :polymorphic => true
     belongs_to :tagger,   :polymorphic => true
 
     validates_presence_of :context
     validates_presence_of :tag_id
 
-    validates_uniqueness_of :tag_id, :scope => [ :taggable_type, :taggable_id, :context, :tagger_id, :tagger_type ]
+    validates_uniqueness_of :tag_id, :scope => [:taggable_type, :taggable_id, :context, :tagger_id, :tagger_type]
 
     after_destroy :remove_unused_tags
 
     # Conditionally adds a counter cache when cache column is present.
-    #   We just regenerate the association. It's the easiest way.
+    #  We just regenerate the association. It's the easiest way.
     # TODO: require the counter cache in release 4.0.0 and remove these methods
     # @see :columns in ActsAsTaggableOn::Taggable::Cache
     def self.columns
       @acts_as_taggable_on_counter_columns ||= begin
         db_columns = super
-        if _has_tags_counter_column?(db_columns)
-          belongs_to :tag, :class_name => 'ActsAsTaggableOn::Tag', :counter_cache => true
-        end
+        belongs_to :tag, :class_name => 'ActsAsTaggableOn::Tag', :counter_cache => ActsAsTaggableOn::Tag.column_names.include?('taggings_count')
         db_columns
       end
     end
 
-    # @private
-    def self._has_tags_counter_column?(db_columns)
-      db_column_names = db_columns.map(&:name)
-      db_column_names.include?("taggings_count")
-    end
+
 
     private
 
     def remove_unused_tags
       if ActsAsTaggableOn.remove_unused_tags
+        # TODO: use taggings_count in release 4.0.0
         if tag.taggings.count.zero?
           tag.destroy
         end