No route matches {:controller=>"comments", :action=>"create"} - It does - ruby-on-rails

Question

Edit: I've seen a number of these but couldn't find an answer to this so I'm attempting to document it as best I can and asking this question.
I have a model-less rails app (calling an API) with a nested comments resource. I am able to post a comment against a story if I go directly to the comments#new or comments#index action and accordingly post to the comments#create action.
However I'd like very much to be able to post a comment on the same page as the #show action of the parent resource: (opusses#show)
I've tried using the rails url_helper path from rake routes as opuss_comments_path and explicitly stating the controller and action. In both cases I still get this message:
No route matches {:controller=>"comments", :action=>"create"}
Here is my routes db:
resources :users
resources :sessions, only: [:new, :create, :destroy]
resources :osessions, only: [:new, :create, :destroy]
resources :authors do
member do
get :following
get :followed
post :follow
end
end
resources :opusses do
resources :comments
member do
get :like
get :authorfeed
post :repost
end
end
And my Rake Routes:
DELETE /authors/:id(.:format) authors#destroy
opuss_comments GET /opusses/:opuss_id/comments(.:format) comments#index
POST /opusses/:opuss_id/comments(.:format) comments#create
new_opuss_comment GET /opusses/:opuss_id/comments/new(.:format) comments#new
edit_opuss_comment GET /opusses/:opuss_id/comments/:id/edit(.:format) comments#edit
opuss_comment GET /opusses/:opuss_id/comments/:id(.:format) comments#show
PUT /opusses/:opuss_id/comments/:id(.:format) comments#update
DELETE /opusses/:opuss_id/comments/:id(.:format) comments#destroy
&&
like_opuss GET /opusses/:id/like(.:format) opusses#like
authorfeed_opuss GET /opusses/:id/authorfeed(.:format) opusses#authorfeed
repost_opuss POST /opusses/:id/repost(.:format) opusses#repost
opusses GET /opusses(.:format) opusses#index
POST /opusses(.:format) opusses#create
new_opuss GET /opusses/new(.:format) opusses#new
edit_opuss GET /opusses/:id/edit(.:format) opusses#edit
opuss GET /opusses/:id(.:format) opusses#show
PUT /opusses/:id(.:format) opusses#update
DELETE /opusses/:id(.:format) opusses#destroy
When I call the code below from comments#index page it works perfectly. However it's quite common to post to another form from a different controller and when I call this code from the opusses#show page it fails with the error above.
On the off chance it had to do with the URL helper, I tried specifying the controller and action explicitly and that still didn't work - generated the same error.

Answer 1

Classic newbie mistake, but for others benefit =>
I had rake routes and I had the path correct, what I wasn't doing was submitting a the id of the parent resource. So POST to the path and include the object in question. In my case this mean opuss_comments_path(#opuss["xyz"]) where xyz was the id of my object.
opuss_comments GET /opusses/:opuss_id/comments(.:format) comments#index
POST /opusses/:opuss_id/comments(.:format) comments#create
Ah.. learning. :)

Answer 2

Based on your routes, You shouldn't have to use a url helper. but you do have to make sure that you have a handle on the Opuss object in the controller. so do something like this ;
#opuss = Opuss.find(params[:id]) #or your equivalent finder code
#comment = #opuss.comments.build
and then in your view;
<%= form_for([#opuss, #comment]) do |f| %>
.... rest of form
<% end %>