File#compute_url() does not consider nested models.

[richardkmichael]

carrierwave-activerecord/lib/carrierwave-activerecord/storage/storage_provider.rb

Line 61 in 0b48c23

url = route_helpers.send(path_method_name, model)

Nested resources need a URL through their parent resource(s), and it must honour the retrieving request's path (in case they belong_to multiple models), ex. /path/via/gallery1/photo/1/file, /path/via/gallery/10/photo/1/file, /path/via/person/5/photo/1/file.

Approaches

1. How can we obtain the request or URL from the controller when inside the model?
   Use Thread.current to store the request. Handled easily by the request_store gem. Then use the Rails router to re-parse the request.url? Or, put only the requisite parts of the parsed request into the Thread local instead of the entire request?
2. Could we decorate the model using ActionView (like FormBuilder) on the way out of the controller?

Can @article.url call a Proc, which is executed with the binding of the view [controller?] to access the request?

def url
  Proc.new do
    # Access the request ... ?  We can capture the request using a Thread local.
  end.call
end