Migration from attachment_fu to paperclip.

migration.rb

class ConvertImagesToPaperclip < ActiveRecord::Migration
  include PaperclipMigrations
 
  def self.up
    # Paperclip 
    add_column :images, :data_file_name, :string
    add_column :images, :data_content_type, :string
    add_column :images, :data_file_size, :integer
    add_column :images, :data_updated_at, :datetime

    # Update table information
    Image.reset_column_information

    # Delete all attachement_fu image sizes
    Image.delete_all("parent_id IS NOT NULL")
    remove_column :images, :parent_id

    # Migrate data
    Image.all.each do |image|
      populate_paperclip_from_attachment_fu(image, image, 'data', 'userimages') if image
      image.reprocess! if image
    end

    # After data migration and paperclip reprocessing remove attachement_fu columns
    remove_column :images, :filename
    remove_column :images, :content_type
    remove_column :images, :size
  end

  def self.down
    raise ActiveRecord::IrreversibleMigration, "Can't recover the deleted data (Image)."
  end

end

paperclip_migrations.rb

module PaperclipMigrations

  def self.included(base)
    base.extend ClassMethods
  end
  
  module ClassMethods
    def populate_paperclip_from_attachment_fu(model, attachment, prefix, path_prefix)
      unless attachment.filename.nil?
        model.send("#{prefix}_file_name=", attachment.filename)
        model.send("#{prefix}_content_type=", attachment.content_type)
        model.send("#{prefix}_file_size=", attachment.size)
        puts "# data_file_name: #{model.send("#{prefix}_file_name")}"
        puts "# data_content_type: #{model.send("#{prefix}_content_type")}"
        puts "# data_file_size: #{model.send("#{prefix}_file_size")}"
 
        # Get file path from attachment_fu
        file_path = ("%08d" % model.id).scan(/..../).join('/')
        old_path = File.join(RAILS_ROOT, 'public', path_prefix, file_path, attachment.filename)
        new_path = model.send(prefix).path(:original)
        new_folder = File.dirname(new_path)
      
        if File.exists?(old_path)
          unless File.exists?(new_folder)
            FileUtils.mkdir_p(new_folder)
          end

          puts "Copying #{old_path} to #{new_path}"
          system("cp #{old_path} #{new_path}")
          model.save
        else
          puts "No such file: #{old_path}"
        end
        puts "# -------- END #"
      end
    end
  end
end