I have ambiguous routes or need to supply additional parameters

Question

I have:

---

in config/routes.rb

map.resources :projects do |project|
  project.resource :privacy
  end
end

---

in models/project.rb

belongs_to :privacy

---

in models/privacy.rb

has_one :project

---

in show.html.haml

= change_privacy_button(@project)

---

in an accessible helper

  def change_privacy_button(project)
      button_builder("24gray/edit.png", "Edit Privacy Settings", edit_project_privacy_path(project), "change_privacy_settings")
  end

---

This is giving me the following error:

Couldn't find Privacy without an ID (ActiveRecord::RecordNotFound)

The error occurs on:

http://localhost:3000/projects/:id/privacy/edit

Rake routes tells me to use:

edit_project_privacy GET
/projects/:project_id/privacy/edit(.:format)
{:action=>"edit", :controller=>"privacies"}

In the debugger, I can summon:

(rdb:1) project
#<Project id: 1...

(rdb:1) project
#<Project id: 1...

(rdb:1) project.privacy
#<Privacy id: 1...

(rdb:1) edit_project_privacy_path
ActionController::RoutingError Exception: edit_project_privacy_url failed to generate from {:action=>"edit", :controller=>"privacies"} - you may have ambiguous routes, or you may need to supply additional parameters for this route.  content_url has the following required parameters: ["projects", :project_id, "privacy", "edit"] - are they all satisfied?

Your thoughts? Thanks! PS, all of the following have also failed:

edit_project_privacy_path(project, project.privacy)

edit_project_privacy_path(project.id, project.privacy)

edit_project_privacy_path(project.privacy_id, project.privacy)

edit_project_privacy_path(project.privacy_id)

edit_project_privacy_path(project.privacy)