The Rails plugin, acts_as_attachment, has recently been improved to not require a filename column in the database. This is useful to anyone who does not want to expose your user’s original filename.

Using acts_as_attachment without filenames is actually very simple. First, your database schema cannot contain a filename column. Second, enhance your class to contain a method to return an appropriate filename. I am using:

def filename
  if parent_id
    "#{parent_id}_#{thumbnail}.file"
  else
    "#{id}.file"
  end
end

As mentioned in my previous post about acts_as_attachment, I am also altering the default directory structure. Putting it all together, here is my attachment model if we were working with the DVD Cover tutorial.

class DvdCover < ActiveRecord::Base
  acts_as_attachment :storage => :file_system,
    :content_type => :image,
    :thumbnails => { :normal => ‘640×480′, :thumb => ‘100×75′ }
  validates_as_attachment

  def filename
    if parent_id
      “#{parent_id}_#{thumbnail}.file”
    else
      “#{id}.file”
    end
  end

  @@HierarchyLevels = 2
  def full_filename(thumbnail = nil)
    object = (thumbnail ? thumbnail_class : self)
    file_system_path = object.attachment_options[:file_system_path]
    parts = [RAILS_ROOT, file_system_path] +
            (1..@@HierarchyLevels).map { |i| partial_path(i) }  +
            [ thumbnail_name_for(thumbnail)]
    File.join(parts)
  end

  protected
  # Given i, extract the ith 8-bit hex representation from our primary id.
  def partial_path(i)
    the_id = (respond_to?(:parent_id) && parent_id) || id
    “%02X” % ((the_id >> (8*i)) % 256)
  end
end