Ruby on Rails - Paperclip and dynamic parameters

Question

I\'m writing some image upload code for Ruby on Rails with Paperclip, and I\'ve got a working solution but it\'s very hacky so I\'d really appreciate advice on how to better imp

Answer 1

I've just solved a similar problem that I had. In my "styles" lambda I am returning a different style depending on the value of a "category" attribute. The problem though is that Image.new(attrs), and image.update_attributes(attrs) doesn't set the attributes in a predictable order, and thus I can't be guaranteed that image.category will have a value before my styles lambda is called. My solution was to override attributes=() in my Image model as follows:

class Image
  ...
  has_attached_file :image, :styles => my_lambda, ...
  ...
  def attributes=(new_attributes, guard_protected_attributes = true)
    return unless new_attributes.is_a?(Hash)
    if new_attributes.key?("image")
      only_attached_file    = {
        "image" => new_attributes["image"]
      }
      without_attached_file = new_attributes
      without_attached_file.delete("image") 
      # set the non-paperclip attributes first
      super(without_attached_file, guard_protected_attributes)
      # set the paperclip attribute(s) after
      super(only_attached_file, guard_protected_attributes)
    else
      super(new_attributes, guard_protected_attributes)
    end
  end
  ...
end

This ensures that the paperclip attribute is set after the other attributes and can thus use them in a :style lambda.

It clearly won't help in situations where the paperclip attribute is "manually" set. However in those circumstances you can help yourself by specifying a sensible order. In my case I could write:

image = Image.new
image.category = "some category"
image.image = File.open("/somefile") # styles lambda can use the "category" attribute
image.save!

(Paperclip 2.7.4, rails 3, ruby 1.8.7)