Rails using a nested path

I have the following:

<%= project_attachment_path(attachment.project, attachment) %>

This outputs: /projects/70/attachments/25

<%= attachment.download_url %>

This outputs: /attachments/25/original.jpg?1291407855

What I want is: /projects/70/attachments/25?original.jpg?1291407855

I tried this: <%= project_attachment_path(attachment.project, attachment.download_url) %>

But that errors? is there a way to make the above work?

Thanks

UPDATING with Download_url method

class Attachment < ActiveRecord::Base
  def download_url(style = nil, include_updated_timestamp = true)
    url = Paperclip::Interpolations.interpolate('/:class/:id/:style.:extension', attachment, style || attachment.default_style)
    include_updated_timestamp && attachment.updated_at ? [url, attachment.updated_at].compact.join(url.incl开发者_如何学运维ude?("?") ? "&" : "?") : url
  end

ROUTES:

resources :projects do
# Download Attachment
get "attachments/:id/:style.:format" => "attachments#download", :as => :attachment
end

resources :attachments do
 collection do
  get 'download', :as => :download
 end
end

Rake Routes:

project_attachment GET    /projects/:project_id/attachments/:id/:style.:format         {:action=>"download", :controller=>"attachments"}

Ok: when you're using this... url = Paperclip::Interpolations.interpolate('/:class/:id/:style.:extension', attachment, style || attachment.default_style)

The '/:class/:id/:style.:extension' portion is what's creating your erroneous URL: /attachments/25/original.jpg?1291407855

I'm not sure exactly the best way to get the "projects/project_id" part into your url, but you need to do something like this:

class Attachment < ActiveRecord::Base
  def download_url(style = nil, include_updated_timestamp = true)

    project_id = self.project.id.to_s

    attachment_url = Paperclip::Interpolations.interpolate('/:class/:id/:style.:extension', attachment, style || attachment.default_style)
    include_updated_timestamp && attachment.updated_at ? [url, attachment.updated_at].compact.join(url.include?("?") ? "&" : "?") : url

    url = 'projects/' + project_id + attachment_url
  end

There may be a more elegant way to do this, but I think this should get you on the right track. Hope it helps!

You can check all the available paths via:

rake routes