Easily change the path for your Paperclip attachments

Today after releasing an app to production environment I saw a couple of paperclip warnings like this in my production.log file:

[paperclip] Duplicate URL for round_image with 
/system/:attachment/:id/:style/:filename. This
will clash with attachment defined in
PageElements::FranchisingCarouselEntry class

This happens because I defined an attachment with the same name in two different models, and the default strategy Paperclip uses to choose attachment locations could lead to filename clashing.

Here is a more detailed example:

class Foo
  has_attached_file :image
end

class Bar
  has_attached_file :image
end

The default strategy Paperclip uses to store attachments relies on this path: /system/:attachment/:id/:style/:filename.

So, considering our example, if we uploaded two files called image.png for the first Foo instance and the first Bar instance, they would have the same path, /system/image/1/original/image.png.

The solution is quite easy; if we add the following line to our config/environment.rb file, Paperclip will add an extra directory level to separate files across different models:

Paperclip::Attachment.default_options[:url] = "/system/:class/:attachment/:id/:style/:filename"

From now on Paperclip will search for files in the system/foo/image/1/original/image.png and system/bar/image/1/original/image.png locations. But we still need to move our previously uploaded files to the new path. We can do this with this rake task:

desc "Copy paperclip data"
task :copy_paperclip_data => :environment do

  def move_images klass, attachment_name
    print "Moving #{attachment_name.pluralize} for #{klass}: "
    instances = klass.find :all
    instances.each do |instance|
      file_name_method = attachment_name + "_file_name"
      unless instance.send(file_name_method).blank?
        filename = Rails.root.join('public', 'system', attachment_name.pluralize, 
          instance.id.to_s, 'original', instance.send(file_name_method))
        if File.exists? filename
          old_attachment_file = File.new filename
          instance.send(attachment_name + "=", old_attachment_file)
          instance.save
          old_attachment_file.close
          print "."
        end
      end
    end
    print " [DONE]"
    puts
  end

  move_images Foo, 'image'
  move_images Bar, 'image'
end

This script is a slightly modified version of the one by Fernando Marcelo you can see here. I changed it a little to make it more verbose and reusable, but big credits go to him for his original work.

Running this rake task with rake copy_paperclip_data will copy all the original files from their old location to the new one.

You will still see the warning messages in your production.log file, because so far Paperclip is not smart enough to check your custom path and understand it is enough to prevent conflicts. This will probably be fixed in future releases of Paperclip gem.