curd on nested resources(the comments resource in rails user guide exmaple)

Hi:

I am following the rails 3 user guide,the blog application.

And I want to make the comment resources editable(and both the create/update form will be displayed in the post/show page),so I try to make the following modifiation(the core):

CommentController.rb:
class CommentsController < ApplicationController
def edit

@post=Post.find(params[:post_id])
@comments=Comment.all
@comment = Comment.find(params[:id])

render "/posts/show"

end

def create

@post = Post.find(params[:post_id])
@comment = @post.comments.create(params[:comment])

respond_to do |format|
  if @comment.save
    format.html { redirect_to post_path @post, notice: 'Comment was successfully saved.' }

    format.json { head :no_content }
  else
    format.html { render "posts/show" }

    format.json { render json: @comment.errors, status: :unprocessable_entity }
  end

end

end

def update

@post=Post.find(params[:post_id])
@comment = Comment.find(params[:id])
respond_to do |format|

  if @comment.update_attributes(params[:comment])
    format.html { redirect_to post_path(@post), notice: 'Comment was successfully updated.' }

    format.json { head :no_content }
  else
    format.html { render "posts/show" }

    format.json { render json: @comment.errors, status: :unprocessable_entity }
  end

end

end
end

post/show.erb.html:

<h2>Comments</h2>
<% @post.comments.each do |comment| %>

<tr>
    <td><%= comment.commenter %></td>
    <td><%= comment.body %></td>

    <td><%= link_to 'Edit', edit_post_comment_path(@post,comment) %></td>
    <td><%= link_to 'Destroy', post_comment_path(@post,comment), confirm: 'Are you sure?', method: :delete %></td>

</tr>
<% end %>

Add a comment:

<%= form_for([@post,@comment]) do |f| %>

<% if @comment.errors.any? %>

<h2><%= pluralize(@comment.errors.count, "error") %> prohibited this comment from being saved:</h2>

<ul>
    <% @comment.errors.full_messages.each do |msg| %>
    <li>

        <%= msg %>
    </li>
    <% end %>

</ul>
<% end %>
<%= f.label :commenter %>
<%= f.text_field :commenter %>
<%= f.label :body %>
<br />
<%= f.text_area :body %>
<%= f.submit %>
<% end %>

routes.rb
resources :posts do

resources :comments
end

The above codes seems work at first,since I can CURD for posts and the nested comments.

However when I create a new comment,if there was any errors in the user input(for example minimum requirement),I will meet the error:

No route matches {:action=>“edit”, :controller=>“comments” …

When I remove the lines:

<%= link_to ‘Edit’, edit_post_comment_path(@post,comment) %>
<%= link_to ‘Destroy’, post_comment_path(@post,comment), confirm: ‘Are you sure?’, method: :delete %>

It will pass, and this error will not occur when I update a comment.

So I wonder why?

BTW,I am afraid I can not express clearly,so I upload the source codes,I hope someone can do me a favor and check it. Thanks.

Bnlog.zip (405 KB)