Paperclip

Automatically detected.

Considering a has_attached_file :asset declaration, all :asset_file_name, :asset_content_type.. columns will be hidden. A file upload field will be created and accessible for customization in the DSL: field :asset, :paperclip.

One thing you may need is a delete method in your model. Paperclip does not include it, you'll need to add it manually. RailsAdmin will detect it and add a checkbox.

class Article < ActiveRecord::Base
  has_attached_file :asset
  # add a delete_<asset_name> method: 
  attr_accessor :delete_asset
  before_validation { self.asset.clear if self.delete_asset == '1' }
end

If you use a :attr_accessible strategy, don't forget to add delete_asset to the whitelist.