Does anybody have any tips for managing polymorphic nested resources in Rails 3?

Question

In config/routes.rb:

resources :posts do
  resources :comments
end

resources :pictures do
  resources :comments
end

I would like to allow for

Answer 1

I had to do something similar in an app of mine. I took what I came up with and changed it around a bit, but I haven't tested it, so use with care. It's not pretty, but it's better than anything else I was able to think of.

In routes.rb:

resources :posts, :pictures

controller :comments do
  get '*path/edit' => :edit, :as => :edit_comment
  get '*path'      => :show, :as => :comment
  # etc. The order of these is important. If #show came first, it would direct /edit to #show and simply tack on '/edit' to the path param.
end

In comment.rb:

embedded_in :commentable, :inverse_of => :comments

def to_param
  [commentable.class.to_s.downcase.pluralize, commentable.id, 'comments', id].join '/'
end

In a before filter in comments_controller.rb:

parent_type, parent_id, scrap, id = params[:path].split '/'

# Security: Make sure people can't just pass in whatever models they feel like
raise "Uh-oh!" unless %w(posts pictures).include? parent_type

@parent = parent_type.singularize.capitalize.constantize.find(parent_id)
@comment = @parent.comments.find(id)

Ok, ugliness over. Now you can add comments to whatever models you want, and simply do:

edit_comment_path @comment
url_for @comment
redirect_to @comment

And so on.

Edit: I didn't implement any other paths in my own app, because all I needed was edit and update, but I'd imagine they'd look something like:

controller :comments do
  get    '*path/edit' => :edit, :as => :edit_comment
  get    '*path'      => :show, :as => :comment
  put    '*path'      => :update
  delete '*path'      => :destroy
end

The other actions will be trickier. You'll probably need to do something like:

  get  ':parent_type/:parent_id/comments'     => :index, :as => :comments
  post ':parent_type/:parent_id/comments'     => :create
  get  ':parent_type/:parent_id/comments/new' => :new,   :as => :new_comment

You'd then access the parent model in the controller using params[:parent_type] and params[:parent_id]. You'd also need to pass the proper parameters to the url helpers:

comments_path('pictures', 7)