如何在帖子的index.html页面中添加评论列表？

Question

How can I add a comment list in my posts' index.html page?

It is my PostsController:

def index
  @posts = Post.all
end

# GET /posts/1
# GET /posts/1.json
def show
  @comments = @post.comments.all
  @comment = @post.comments.build
end

and its my posts show view:

<p id="notice"><%= notice %></p>

<p>
  <h3><%= @post.name %></h3>
</p>

<p>
  <%= (@post.descriptopm).html_safe %>
</p>

<%= link_to 'Edit', edit_post_path(@post), :class => "btn btn-info btn-xs" %>
<%= link_to 'Back', posts_path, :class => "btn btn-info btn-xs" %>

<h3>Comments</h3>
<% @comments.each do |comment| %>
  <div>
    <strong><%= comment.user_name %></strong>
    <br />
    <p><%= (comment.body).html_safe %></p>
  </div>
<% end %>
<%= render 'comments/form' %>

and its my posts index view:

<h1>Listing posts</h1>
<%= link_to 'Create a New Post', new_post_path, :class => "btn btn-success btn-sm" %>
<% @posts.each do |post| %>
<div class="post thumbnail">
  <h3><%= post.name %></h3>
  <div><%= (post.descriptopm).html_safe %></div>

  <div class="bottom-bottoms">
    <%= link_to 'Display', post, :class => "btn btn-info btn-xs" %>
    <%= link_to 'Edit', edit_post_path(post), :class => "btn btn-info btn-xs" %>
    <%= link_to 'Delete', post, method: :delete, data: { confirm: 'Are you sure?' }, :class => "btn btn-info btn-xs" %>
  </div>

  <h3>Comments</h3>
  <% @post.comments.each do |comment| %>
    <div>
      <strong><%= comment.user_name %></strong>
      <br />
      <p><%= (comment.body).html_safe %></p>
    </div>
  <% end %>
  <%= render 'comments/form' %>

</div>
<% end %>

the post.rb :

class Post < ActiveRecord::Base
    has_many :comments
end

the comment.rb :

class Comment < ActiveRecord::Base
    belongs_to :post
end

the show page show the comments well but the index cannot... it shows the error : undefined method `comments' for # please help me >"< I am a newly Ruby on Rails writer

Answer 1

instead of using @post in comment use post on index page. You have typo error.

<%= link_to 'Create a New Post', new_post_path, :class => "btn btn-success btn-sm" %>
<% @posts.each do |post| %>
<div class="post thumbnail">
  <h3><%= post.name %></h3>
  <div><%= (post.descriptopm).html_safe %></div>

  <div class="bottom-bottoms">
    <%= link_to 'Display', post, :class => "btn btn-info btn-xs" %>
    <%= link_to 'Edit', edit_post_path(post), :class => "btn btn-info btn-xs" %>
    <%= link_to 'Delete', post, method: :delete, data: { confirm: 'Are you sure?' }, :class => "btn btn-info btn-xs" %>
  </div>

  <h3>Comments</h3>
  <% post.comments.each do |comment| %>
    <div>
      <strong><%= comment.user_name %></strong>
      <br />
      <p><%= (comment.body).html_safe %></p>
    </div>
  <% end %>
  <%= render 'comments/form' %>

</div>
<% end %>

Answer 2

Associations

If you're using ActiveRecord association to "link" your Post and Comment model, you'll be able to call .comments on each post you have in your index

Something to note (and this lies at the core of your error) is that you will have to call the .comments method on each instance of the Post . You're currently trying to call it on an @instance variable which doesn't exist:

#app/views/posts/index.html.erb
<% @posts.each do |post| %>
   <% post.comments.each do |comment| %>
      <%= comment.body %>
   <% end %>
<% end %>

This, of course, is only possible by using the setup you have already ( has_many / belongs_to ):

#app/models/post.rb
Class Post < ActiveRecord::Base
   has_many :comments #-> post.comments
end

#app/models/comment.rb
Class Comment < ActiveRecord::Base
   belongs_to :post #-> comment.post
end