gistfile1.rb

  desc "Moves files to a new :path NB! backup your files before use this task (set CLASS and PATH, ATTACHMENT is optional)"
  task :change_path => :environment do
    raise 'PATH must be specified, like PATH=:rails_root/public/system/:class/:attachment/:style/:id.:extension' if ENV['PATH'].blank?
    path = ENV['PATH']
    for_all_attachments do |instance, name|
      object = instance.send(name)
      old_path = object.instance_variable_get :'@path'
      
      styles = [:original] + object.styles.keys
      
      styles.each do |style|
        if object.exists?(style)
          object.queued_for_write[style] = object.to_file(style)
        end
      end

      object.instance_variable_set :'@path', path
      object.flush_writes

      object.instance_variable_set :'@path', old_path
      object.instance_variable_set :'@queued_for_delete', styles.map { |style| object.path(style) }
      object.flush_deletes

      # if stopped working then use:
      # path = Paperclip::Interpolations.interpolate(path, object, style)
      # and own write and delete functions
    end
  end