Question

我是ruby on rails的新手，并且知道这是一个初学者错误。我正在尝试创建一个在帖子中显示用户评论的应用程序。我有一个评论部分指向我的帖子#show，并且当请求显示＆lt;％= image_tag（comment.user.avatar.small.url，class：“media-object”）时，如果comment.user.avatar？％GT;来自_comment.html.erb，我为nil获取了“未定义的方法'用户'：NilClass。我已经阅读了有关stackoverflow的其他问题，我知道这说它找不到与评论中的帖子关联的用户，而且我需要在我的控制器中定义用户。我假设它是用于后置控制器，但我似乎无法用特定的语法来解决用户在帖子中显示注释。

#comments_controller
def create
 @topic = Topic.find(params[:topic_id])
 @post = Post.find(params[:post_id])
 @comment = current_user.comments.new(comment_params)
 @comment.post = @post
 @comment.save
 authorize @comment
 redirect_to [@topic, @post]
end

#posts_controller
def show
 @topic = Topic.find(params[:topic_id])
 @post = Post.find(params[:id]) 
end

#post model
class Post < ActiveRecord::Base
 belongs_to :user
 belongs_to :topic
 has_one :summary
 has_many :comments
 mount_uploader :image, ImageUploader

#comment model
 class Comment < ActiveRecord::Base
  belongs_to :post
  belongs_to :user

#rendering comment partial in post#show
 <h1><%= @post.markdown_title %></h1>
 <div class="row">
  <div class="col-md-8">
   <small>
    <%= image_tag(@post.image.thumb.url) if @post.image? %></br>
    <%= image_tag(@post.user.avatar.tiny.url) if @post.user.avatar? %>
  submitted <%= time_ago_in_words(@post.created_at) %> ago by
   <%= @post.user.name %>
  </small>
  <p><%= @post.markdown_body %></p>
 </div>

<div class="col-md-4">
 <% if policy(@post).edit? %>
  <%= link_to "Edit", edit_topic_post_path(@topic, @post), class: 'btn btn-success' %> 
<% end %>
<% if policy(@post).destroy? %>
  <%= link_to "Delete Post", [@topic, @post], method: :delete, class: 'btn btn-danger', data: { confirm: "Are you sure you want to delete this post?" }  %>
  <% end %>
</div>

<div class="col-md-8">
 <% if policy(Comment.new).create? %>
   <%= render partial: 'comments/comment', locals: { comment: @comment } %>
   <%= render partial: 'comments/form', locals: {topic: @topic, post: @post} %>
<% else %>
  <h3>Sign up to Bloccit to post comments</h3>
  <%= link_to "Sign up", new_user_registration_path, class: 'btn btn-primary' %></br></br>
<% end %>

#comment partial
 <ul>
 <% @post.comments.each do |c| %>
  <div class="media">
   <div class="media-left">
    <%= image_tag(comment.user.avatar.small.url, class: "media-object") if comment.user.avatar? %>
   </div>
   <div class="media-body">
    <small>
     <%= comment.user.name %> commented <%= time_ago_in_words(comment.created_at) %> ago
  <% if policy(comment).destroy? %>
    | <%= link_to "Delete", [@topic, @post, comment], method: :delete %>
   <% end %>
   </small>
 <li>
  <p><%= c.body %></p>
</li>
</div>
<% end %>

另外，当我在posts_controller中输入@ post.user = @user时，错误更改为“未定义的方法'avatar'为nil：NilClass。感谢您的帮助！

Answer 1

您错误地引用了块变量。将|c|更改为|comment|或将comment引用更改为c。

所以这样：

<%= image_tag(c.user.avatar.small.url, class: "media-object") if c.user.avatar? %>

Answer 2

未定义的方法'user'代表nil：NilClass

错误是因为这行

<%= render partial: 'comments/comment', locals: { comment: @comment } %>

您没有@comment show方法初始化posts_controller，而locals的{{1}}传递comment，comment.user _comment.html.erb }返回错误。

而且我也注意到<% @post.comments.each do |c| %>你有c这一行，所以你可以使用comment代替<%= image_tag(c.user.avatar.small.url, class: "media-object") if c.user.avatar? %>。

def rfind(lst, condition):
    return next((len(lst) - n
                 for (n, i) in enumerate(reversed(lst), 1)
                 if condition(i)),
                -1) # If we couldn't find anything, return -1

>>> lst = ['{b}', '[c]', '{a}', 'g']
>>> print rfind(lst, lambda i: '{' in i)
2
>>> print rfind(lst, lambda i: 'q' in i)
-1

在partials中定义用户

2 个答案: