Rails Engines: Namespaced Polymorphic URLs

Question

I have a Rails engine, MyEngine, that doesn't have an isolated namespace. I'm trying to use the polymorphic helpers to generate links to resources, as per the docs.

An engine route:

# config/routes.rb
...
  namespace :admin do
    resources :my_resource
  end
...

Example output of rake app:routes (remember, this is an Engine):

    admin_my_resources GET    /admin/my_resources(.:format)          my_engine/admin/my_resources#index
                       POST   /admin/my_resources(.:format)          my_engine/admin/my_resources#create
 new_admin_my_resource GET    /admin/my_resources/new(.:format)      my_engine/admin/my_resources#new
edit_admin_my_resource GET    /admin/my_resources/:id/edit(.:format) my_engine/admin/my_resources#edit
     admin_my_resource PUT    /admin/my_resources/:id(.:format)      my_engine/admin/my_resources#update
                       DELETE /admin/my_resources/:id(.:format)      my_engine/admin/my_resources#destroy

If my_resource is an instance of a MyResource model with ID 12345, I'd expect:

polymorphic_url([my_engine, :admin, my_resource])

to render:

/my_engine/admin/my_resource/12345

but I was wrong. Instead, I get an exception:

undefined method `admin_my_engine_my_resource_path'...

So, polymorphic_url is trying to use admin_my_engine_my_resource_path where it really should be using something more like my_engine.admin_my_resource_path(my_resource)

Rails seems to be adding :admin the wrong way around... or am I doing it wrong?

Hirschfeld

Answer 1

Have you tried doing this via a scope instead of a namespace?

See this SO article for a better explanation. Rails Scoped Routing

A good example of this is the devise gem.

Good luck!

Like

Your answer spurred me to look closer at the namespace and scope and I've ended up creating scopes such as scope module: "admin", as: "admin" to get around it. Thanks! – Hirschfeld

Answer 2

Run rake routes and get the url helper function name from there. You can share the rake routes output here also.

Makeyevka

I need the polymorphic route helpers to work. Calling my_engine.admin_my_resource(my_resource) works nicely but the equivalent using polymorphic_url does not. I'll edit my question to be a bit clearer. – Hirschfeld

Just for clarification. Does polymorphic_url([:my_engine, :admin, my_resource]) work? Just symbolizing the my_engine. I cant test this in my machine right now so asking you :) – Makeyevka

Answer 3

I recently came across this problem in Rails 5, and found the following general solution.

Given my engine called YamsCore, which generates usual url helpers in form :

url_for(yams_core.album_tracks_path)

You can write a generic view helper accepting ANY model and generate urls via :

path = polymorphic_path([view.yams_core, my_resource])

and if you need to specify the action

path = polymorphic_path([view.yams_core, my_resource], action: :edit)

i.e.

path = polymorphic_path([view.engine_prefix, my_resource])

Sancha