Add a helper that creates the Paperclip columns

    This can be used in migrations, i.e.

      create_table :users do |t|
        t.has_attached_file :avatar
      end

(three commits squashed into one by Alexey Mahotkin <squadette@gmail.com>)

README.md

@@ -80,17 +80,13 @@ In your migrations:
 
     class AddAvatarColumnsToUser < ActiveRecord::Migration
       def self.up
-        add_column :users, :avatar_file_name,    :string
-        add_column :users, :avatar_content_type, :string
-        add_column :users, :avatar_file_size,    :integer
-        add_column :users, :avatar_updated_at,   :datetime
+        change_table :users do |t|
+          t.has_attached_file :avatar
+        end
       end
 
       def self.down
-        remove_column :users, :avatar_file_name
-        remove_column :users, :avatar_content_type
-        remove_column :users, :avatar_file_size
-        remove_column :users, :avatar_updated_at
+        drop_attached_file :users, :avatar
       end
     end
 

lib/paperclip/railtie.rb

 require 'paperclip'
+require 'paperclip/schema'
 
 module Paperclip
   if defined? Rails::Railtie
@@ -21,6 +22,9 @@ module Paperclip
       File.send(:include, Paperclip::Upfile)
 
       Paperclip.options[:logger] = defined?(ActiveRecord) ? ActiveRecord::Base.logger : Rails.logger
+
+      ActiveRecord::ConnectionAdapters::Table.send(:include, Paperclip::Schema)
+      ActiveRecord::ConnectionAdapters::TableDefinition.send(:include, Paperclip::Schema)
     end
   end
 end

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
+    end
+  end
+end