rubyonrailsin

I am working through the official Getting Started with Rails tutorial
http://guides.rubyonrails.org/getting_started.html#generating%20-a-controller

I am stuck on section 8.4 Generating a Controller. It suggests there
that this definition:
def index
@post = Post.find(params[:post_id])
@comments = @post.comments
end

S ould be used in com ents_controller.rb. Surely that would make
http://localhost:3000/comments work, but it gives the error
Couldn't find Post without an ID. That suggests a problem with the first
line of the definition. However that is what it says I should use in the
tutorial so I looked at post.rb and comment.rb and they are as directed.
Also checked routes.rb but all seems to be correct. Incidentally the
page http://localhost:3000/posts/1
works fine and displays comments which I have to enter with the terminal
as http://localhost:3000/comments/new gives the same error.

I have been tearing my hair out with this for 3 days. Can somebody
please point out what I am doing wrong.

Attachments:
http://www.ruby-forum.com/attachment/4577/index.html.erb

--
Posted via http://www.ruby-forum.com/.

--
You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group.
To post to this group, send email to rubyonrails-talk@googlegroups.com.
To unsubscribe from this group, send email to rubyonrails-talk+unsubscribe@googlegroups.com.
For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en.