Migration from attachment_fu database storage to paperclip

paperclip_migrations.rb

module PaperclipMigrations

  def self.included(base)
    base.extend ClassMethods
  end

  module ClassMethods
    def add_paperclip_fields(table, prefix)
      add_column table, "#{prefix}_file_name", :string
      add_column table, "#{prefix}_content_type", :string
      add_column table, "#{prefix}_file_size", :integer
      add_column table, "#{prefix}_updated_at", :datetime
    end

    def remove_attachment_fu_fields(table)
      remove_column table, :filename
      remove_column table, :content_type
      remove_column table, :size
      remove_column table, :db_file_id
    end

    def populate_paperclip_from_attachment_fu(model, prefix)
      Object.const_set(:DbFile, Class.new(ActiveRecord::Base)) unless Object.const_defined?(:DbFile)
      model.class.belongs_to  :db_file, :class_name => '::DbFile', :foreign_key => 'db_file_id' unless model.respond_to?(:db_file)

      unless model.filename.nil?
        model.send("#{prefix}_file_name=", model.filename)
        model.send("#{prefix}_content_type=", model.content_type)
        model.send("#{prefix}_file_size=", model.size)
        model.save

        new_path = model.send(prefix).path(:original)
        new_folder = File.dirname(new_path)

        unless File.exists?(new_folder)
          FileUtils.mkdir_p(new_folder)
        end

        if model.db_file
          puts "Writing to #{new_path}"
          File.open(new_path, 'w') { |f| f.puts model.db_file.data }
          model.send(prefix).reprocess!
        else
          puts "No data for: #{model.inspect}"
        end
      end
    end
  end
end