Ruby/Rails: How do I insert the post_id w/user_id?

Question

I read this post and it was helpful for the first step, now I'm at the second step. I need help with the controllers and forms.

Let's say this is my model:

User
 has_many :posts
 has_many :comments

Post
 belongs_to :user
 has_many :comments

Comment
 belongs_to :user
 belongs_to :post

And these are my tables:

User
 id

Post
 id
 user_id

Comment
 id
 user_id
 post_id

In the initial post, the User ID gets added with the content automatically by adding this to the create section in the controller:

@post = current_user.post.build(params[:post])

If the comment belongs to both the user and the post, how do I make it automatically add the post_id as well as the user_id? Currently, I can only seem to make it insert the user_id by doing this:

current_user.comments.build(params[:comment])

I'm new to rails. I don't think the best way would be to make the field accessible and add a hidden field in the form, isn't there another way?

These are my updated routes:

                  users GET    /users(.:format)                                           users#index
                        POST   /users(.:format)                                           users#create
               new_user GET    /users/new(.:format)                                       users#new
              edit_user GET    /users/:id/edit(.:format)                                  users#edit
                   user GET    /users/:id(.:format)                                       users#show
                        PUT    /users/:id(.:format)                                       users#update
                        DELETE /users/:id(.:format)                                       users#destroy
               sessions POST   /sessions(.:format)                                        sessions#create
            new_session GET    /sessions/new(.:format)                                    sessions#new
                session DELETE /sessions/:id(.:format)                                    sessions#destroy
   Post_comments GET    /posts/:Post_id/comments(.:format)          comments#index
                        POST   /posts/:Post_id/comments(.:format)          comments#create
 new_Post_Comment GET    /posts/:Post_id/comments/new(.:format)      comments#new
edit_Post_Comment GET    /posts/:Post_id/comments/:id/edit(.:format) comments#edit
     Post_Comment GET    /posts/:Post_id/comments/:id(.:format)      comments#show
                        PUT    /posts/:Post_id/comments/:id(.:format)      comments#update
                        DELETE /posts/:Post_id/comments/:id(.:format)      comments#destroy
          posts GET    /posts(.:format)                                   posts#index
                        POST   /posts(.:format)                                   posts#create
       new_Post GET    /posts/new(.:format)                               posts#new
      edit_Post GET    /posts/:id/edit(.:format)                          posts#edit
           Post GET    /posts/:id(.:format)                               posts#show
                        PUT    /posts/:id(.:format)                               posts#update
                        DELETE /posts/:id(.:format)                               posts#destroy
                   root        /                                                          static_pages#home
                 signup        /signup(.:format)                                          users#new
                 signin        /signin(.:format)                                          sessions#new
                signout DELETE /signout(.:format)                                         sessions#destroy
                  start        /start(.:format)                                           posts#new

Answer 1

The best way that I've found to do commenting has been covered by Ryan Bates on railscasts here

class Comment < ActiveRecord::Base
  attr_accessible :content
  belongs_to :commentable, polymorphic: true
end

class Post < ActiveRecord::Base
  attr_accessible :content, :name
  has_many :comments, as: :commentable
end

And you can pass current_user when actually building the comments in the controller, or pass it as a hidden field, a few different options available to you.

Edit for routes: Ah that's why, you're comments and your posts aren't hooked into each other at all. in your routes where you do resources :post change it do

resources :post do 
  resources :comments 
end

You need to associate the comments to the posts if you're doing Post.comments.build If you're doing current_user.comments.build you'll need to do this in your routes

resources :user do
  resources :comments
end