Ruby on rails:如何在不刷新页面的情况下发布评论

Question

• 我正试图使用rails 6和jQuery实现评论功能，但我希望用户可以在不刷新浏览器的情况下向帖子添加评论，我创建了一个comment_controller.rb和模型comment.rb，

• 然后我通过has_many:comments将帖子、用户和评论模型关联起来，并属于用户和帖子，但问题是当我试图创建帖子时，我发现了这个错误：

app/controllers/comments_controller.rb:8:in `create'
Started POST "/comments" for ::1 at 2021-06-10 09:56:42 +0200
Processing by CommentsController#create as JS
Parameters: {"comment"=>{"user_id"=>"1", "body"=>"good one ;)"}, "commit"=>"Post"}
(3.8ms)  SELECT sqlite_version(*)
User Load (15.0ms)  SELECT "users".* FROM "users" WHERE "users"."id" = ? ORDER BY "users"."id" ASC LIMIT ?  [["id", 1], ["LIMIT", 1]]
TRANSACTION (0.1ms)  begin transaction
↳ app/controllers/comments_controller.rb:11:in `create'
User Load (0.5ms)  SELECT "users".* FROM "users" WHERE "users"."id" = ? LIMIT ?  [["id", 1], ["LIMIT", 1]]
↳ app/controllers/comments_controller.rb:11:in `create'
TRANSACTION (0.1ms)  rollback transaction
↳ app/controllers/comments_controller.rb:11:in `create'
Rendering comments/create.js.erb
Rendered comments/create.js.erb (Duration: 294.2ms | Allocations: 1386)
Completed 500 Internal Server Error in 7130ms (ActiveRecord: 105.2ms | Allocations: 21119)
ActionView::Template::Error (undefined method `comments' for nil:NilClass):
1:
2: $('#comment_pane').append("<%= j render @post.comments.last %>");
3: $('#comment_body').val('');
app/views/comments/create.js.erb:2

• 这是我的评论控制器.rb：

  class CommentsController < ApplicationController
  before_action :authenticate_user!
  def create  
  @comment = Comment.new(comment_params)
  @comment.user_id = current_user.id if user_signed_in?
  @comment.save           
  end
  def destroy 
  @comment.destroy  
  end
  private
  def comment_params
  params.require(:comment).permit(:body, :user_id, :post_id)
  end
  end
  

• 这是我的index.html.erb中的评论行：

  <div id="comment_pane" class=" comment-box " >
  <%= render "comments/comments", post: post %>
  </div>
  <div class="bottom border-t pt-3 mt-3">
  <%= render  'comments/form' %>
  </div>
  

• this _form.html.erb:

  <%= form_for Comment.new, remote: true  do |f| %>
  <%= f.hidden_field :user_id, value: current_user.id %>
  <%= f.text_field :body, placeholder: "add comment here ..." %>
  <%= f.submit "Post", class: "comment-button text-blue-500 opacity-75 w-2/12 text-center font-bold", autocomplete: :off %>
  <% end %>
  

• create.js.erb:

  $('#comment_pane').append("<%= j render @post.comments.last %>");
  $('#comment_body').val('');
  

• 我面临的问题是，在用户提交评论后，我发现了这个错误：

undefined method `comments' for nil:NilClass  
app/views/comments/create.js.erb:2

请帮忙吗？

Answer 1

您收到错误，因为您的视图期望@post存在，但它尚未定义。您可以修改CommentsController#create以包含创建的评论的帖子。

class CommentsController < ApplicationController
def create  
@comment = Comment.new(comment_params)
@comment.user_id = current_user.id if user_signed_in?
@comment.save
@post = @comment.post # or Post.find(comment_params[:post_id])
end
end