Refactor the implementation of the schema helpers

lib/paperclip/schema.rb

 module Paperclip
   module Schema
-    def has_attached_file(name)
-      column :"#{name}_file_name",    :string
-      column :"#{name}_content_type", :string
-      column :"#{name}_file_size",    :integer
-      column :"#{name}_updated_at",   :datetime
+    @@columns = {:file_name    => :string,
+                 :content_type => :string,
+                 :file_size    => :integer,
+                 :updated_at   => :datetime}
+
+    def has_attached_file(attachment_name)
+      @@columns.each do |name, type|
+        column_name = full_column_name(attachment_name, name)
+        column(column_name, type)
+      end
+    end
+
+    def drop_attached_file(table_name, attachment_name)
+      @@columns.each do |name, type|
+        column_name = full_column_name(attachment_name, name)
+        remove_column(table_name, column_name)
+      end
     end
 
-    def drop_attached_file(table_name, name)
-      remove_column table_name, :"#{name}_file_name"
-      remove_column table_name, :"#{name}_content_type"
-      remove_column table_name, :"#{name}_file_size"
-      remove_column table_name, :"#{name}_updated_at"
+    protected
+
+    def full_column_name(attachment_name, column_name)
+      "#{attachment_name}_#{column_name}".to_sym
     end
   end
 end