How to: Do conditional processing

NOTE: Not included in latest gem release (0.5.4)

If you want to hold both images and regular files as attachments to a model, additional processing (i.e. creating a thumbnail) can be attached only to images.

Here's the example code to create thumbnails when the uploaded file is an image:

version :thumb, :if => :image? do
  process :resize_to_limit => [200, 200]
end

protected

def image?(new_file)
  new_file.content_type.include? 'image'
end

Just a mention, to avoid multiple checking if it is needless in your case, you could make it like as:

your_model.rb:

attr_proccessor :is_thumbnable

your_uploader.rb:

def image?(new_file)
  return model.is_thumbnable unless model.is_thumbnable.nil?
  model.is_thumbnable = \
    begin
      #your condition goes here and it should return true or false, except nil
    end
end