Ruby on Rails 5嵌套注释未创建

Question

I'm a beginner in rails and trying to create a Reddit type blog page. Currently, I'm working on nested comments so the user is able to reply to comments. In my app I have forums, posts and comments. Creating posts and forums has worked perfectly, also posting comments until I tried nesting replies. My code looks like this (Forums and Users models/controllers have been omitted) :

My Comment model:

class Comment < ApplicationRecord
 belongs_to :commentable, polymorphic: true
 belongs_to :user
 has_many :comments, as: :commentable
end`

My Post model:

class Post < ApplicationRecord
 belongs_to :forum
 belongs_to :user
 has_many :comments, as: :commentable, dependent: :destroy
end

My posts_controller:

class PostsController < ApplicationController

def index
 @posts = Post.all
end

def show
 @post = find_post
end

def new
 @post = Post.new
end

def edit
 @post = find_post
end

def create
 @forum = Forum.find(params[:forum_id])
 @post = @forum.posts.create(post_params.merge(user_id: current_user.id))
 redirect_to forum_path(@forum)
end

def update
 @post = find_post

 if @post.update(post_params)
  redirect_to forum_path
 else
  render 'show'
 end
end

def destroy
 @post = find_post
 @post.destroy

 redirect_to forum_path
end

private
 def post_params
  params.require(:post).permit(:title, :content)
 end

private
 def find_post
  @forum = Forum.find(params[:forum_id])
  @forum.posts.find(params[:id])
 end
end

My comments_controller:

class CommentsController < ApplicationController
 before_action :find_commentable

 def index
  @comments = Comment.all
 end

 def new
  @comment = Comment.new
 end

 def create
  @comment = @commentable.comments.create(comment_params.merge(user_id:        current_user.id))
  if @comment.save
   @post = Post.find_by_id(params[:post_id])
   redirect_to forum_post_path(@post.forum_id, @post), notice: 'Your comment was successfully posted!'
  else
   redirect_to forum_post_path(@post.forum_id, @post), notice: 'error :('
  end
 end

 private
  def comment_params
   params.require(:comment).permit(:content)
  end

private
 def find_commentable
  @commentable = Comment.find_by_id(params[:comment_id]) if params[:comment_id]
  @commentable = Post.find_by_id(params[:post_id]) if params[:post_id]
 end
end

My views/comments/_comment:

<li>
<%= comment.content %>
<small>Submitted <%= time_ago_in_words(comment.created_at) %> ago</small>

<h2>Add a Reply:</h2>
 <%= form_with(model: [ comment, comment.comments.build ], local: true) do |form| %>
  <p>
    <%= form.text_area :content, placeholder: "Add a Reply" %><br/>
    <%= form.submit %>
  </p>
 <% end %>
<ul>
  <%= render partial: 'comments/comment', collection: comment.comments if comment.comments.any? %>
</ul>
<%= link_to 'Back', forum_post_path(@forum, @post) %>

My views/post/show:

<small>Submitted <%= time_ago_in_words(@post.created_at) %> ago</small>

<h3>Comments</h3>

<ul>
 <%= render(partial: 'comments/comment', collection: @post.comments) if @post.comments.any?%>
</ul>

<h2>Add a comment:</h2>

<%= form_with(model: [ @post, @post.comments.build ], local: true) do |form| %>
<%= form.text_field :content, placeholder: "Add a comment" %><br/>
<%= form.submit "Add Comment" %>
<% end %>

<%= link_to 'Back', forum_path(@forum) %>
<%= link_to 'All posts', forum_posts_path(@post.forum_id) %>
<%= link_to 'All comments', post_comments_path(@post) %>

</li>

My routes:

  resources :posts do
   resources :comments
  end

  resources :comments do
   resources :comments
  end

The first errors I kept getting were that every time I submitted a comment in view/posts/show the comment wouldn't create. Now, views/comments/_comment lifts the error:

Showing /example/app/views/comments/_comment.html.erb where line #3 raised:

nil can't be converted to a Time value 

<small>Submitted <%= time_ago_in_words(comment.created_at) %> ago</small>

after I submit a new comment. Any help regarding this error is appreciated or related to my main goal, I have been circling around this for a long time. Thanks!

Answer 1

The problem here is that new comment is initialized(for the comment which is being rendered) every time the partial is trying to render the comment. Check out the following byebug output:

(byebug) pp comment.comments
[#<Comment:0x007f35ce11d900
  id: 5,
  content: "DEF",
  commentable_id: 4,
  commentable_type: "Comment",
  user_id: 1,
  created_at: Wed, 30 May 2018 06:53:51 UTC +00:00,
  updated_at: Wed, 30 May 2018 06:53:51 UTC +00:00>,
 #<Comment:0x007f35ce2a3388
  id: nil,
  content: nil,
  commentable_id: 4,
  commentable_type: "Comment",
  user_id: nil,
  created_at: nil,
  updated_at: nil>]

This line is the culprit:

 <%= form_with(model: [ comment, comment.comments.build ], local: true) do |form| %>

comment.comments.build initializes a new empty Comment which is your code then tries to render and throws the error as it does not have created_at .

And then the newly initialized comment is being rendered by the code.

Replacing app/views/comments/_comment#13 with the following will resolve the issue:

  <%= render(partial: 'comments/comment', collection: comment.comments.where.not(content: nil)) if comment.comments.any? %>