如果验证失败，则为评论显示错误

Question

我有一个登录用户可以向帖子添加评论的表单。这是我在我的文件中的代码，到目前为止：

# views/posts/show.html.haml 
%h3 This post has #{ pluralize(@post.comments.count, "comment") } 
= render @post.comments # views/comments/_comment.html.haml 
= render "comments/form" 

# views/comments/_comment.html.haml - list all comments of the post 
.media 
    .media-body 
    %h4.media-heading 
     = comment.user.name 
     %small added #{time_ago_in_words comment.created_at} ago 
    %p= comment.body 
%hr 

# views/comments/_form.html.haml 
- if user_signed_in? 
    = errors_for @comment if @comment # errors_for is just a custom helper I've created to loop through all validation errors 

    = form_for([@post, Comment.new]) do |f| 
    .form-group 
     = f.label :body, "Leave a comment" 
     = f.text_area :body, class: "form-control", rows: "6" 
    .form-group 
     = f.submit "Add", class: "btn btn-primary" 

# controllers/comments_controller.rb 
def create 
    @post = Post.find(params[:post_id]) 

    @comment = @post.comments.create(params[:comment].permit(:body).merge(:user => current_user)) 

    if @comment.errors.any? 
     render "posts/show" 
    else 
     redirect_to post_path(@post) 
    end 

    # have also tried this way too 
    # @comment = @post.comments.build(params[:comment].permit(:body)) 
    # @comment.user = current_user 
    # if @comment.save 
    # redirect_to post_path(@post) 
    # else 
    # render "posts/show" 
    # end 
end 

当我点击提交按钮来添加与形式是空的（需要注释的身体），我得到这个奇怪的错误评论（更好的错误宝石）

NoMethodError at /posts/1/comments 

undefined method `>' for nil:NilClass 

和特色_comment.html.haml这行代码%small added #{time_ago_in_words comment.created_at} ago。另外，如预期的那样，将postID和userID分配给@comment，并且comment.body和created_at和updated_at是预期的。

我已经暂时从这个文件中删除了所有ruby嵌入代码，并且一切正常 - 除了从我没有得到评论列表的事实 - 验证按预期工作，我可以看到我的错误屏幕。

我该如何解决这个问题？

编辑

工作正常，但是我在同一件事情挣扎。如果帖子已经有一些旧评论，我会收到N + 1查询正在运行的警告。

N+1 Query detected 
    Comment => [:user] 
    Add to your finder: :includes => [:user] 
N+1 Query method call stack 
    /app/views/comments/_comment.html.haml:5:in `_app_views_comments__comment_html_haml__3499194119219243109_33739760' 
    /app/views/posts/show.html.haml:23:in `_app_views_posts_show_html_haml__2205508389884571191_36379560' 
    /app/controllers/comments_controller.rb:10:in `create' 

/app/views/comments/_comment.html.haml:5:in `_app_views_comments__comment_html_haml__3499194119219243109_33739760' 
/app/views/posts/show.html.haml:23:in `_app_views_posts_show_html_haml__2205508389884571191_36379560' 
/app/controllers/comments_controller.rb:10:in `create' 

我知道这是脱离主题，但任何想法如何解决这个问题？我在哪里需要使用.includes(:user) ??

Answer 1

正如您已经声明“created_at ... is nil”。即使你的代码行被注释掉了，它仍然会被erb评估，导致time_ago_in_words抛出零例外。这将是更好的使用条件语句，如：

# views/comments/_comment.html.haml - list all comments of the post 
.media 
    .media-body 
    %h4.media-heading 
     = comment.user.name 
     - if comment.created_at.present? 
     %small added {time_ago_in_words comment.created_at} ago 
     - else 
     % small comment not yet been created 
    %p= comment.body 
%hr