Account::Posts#index 中的 NoMethodError

Question

我正在做 Ruby101 教程，但遇到了一些问题。

rails日志：

ActionView::Template::Error (undefined method `title' for nil:NilClass):
13:       <% @posts.each do |post| %>
14:         <tr>
15:           <td> <%= post.content %> </td>
16:           <td> <%= post.group.title %> </td>
17:           <td> <%= post.updated_at %> </td>
18:           <td> <%= link_to('Edit', edit_group_post_path(post.group, post), class: "btn btn-default btn-xs") %></td>
19:           <td> <%= link_to('Delete', group_post_path(post.group, post), method: :delete, data: { confirm: "Are you sure?" }, class: "btn btn-default btn-xs") %></td>

app/views/account/posts/index.html.erb:16:in block in _app_views_account_posts_index_html_erb___92982360307258762_69918747126320' app/views/account/posts/index.html.erb:13:in_app_views_account_posts_index_html_erb___92982360307258762_69918747126320' Rendering /home/zedong/.rvm/gems/ruby-2.3.1/gems/actionpack-5.0.0.1/lib/action_dispatch/middleware/templates/rescues/template_error.html.erb within rescues/layout Rendering /home/zedong/.rvm/gems/ruby-2.3.1/gems/actionpack-5.0.0.1/lib/action_dispatch/middleware/templates/rescues/_source.html.erb Rendered /home/zedong/.rvm/gems/ruby-2.3.1/gems/actionpack-5.0.0.1/lib/action_dispatch/middleware/templates/rescues/_source.html.erb (3.7ms) Rendering /home/zedong/.rvm/gems/ruby-2.3.1/gems/actionpack-5.0.0.1/lib/action_dispatch/middleware/templates/rescues/_trace.html.erb Rendered /home/zedong/.rvm/gems/ruby-2.3.1/gems/actionpack-5.0.0.1/lib/action_dispatch/middleware/templates/rescues/_trace.html.erb (2.5ms) Rendering /home/zedong/.rvm/gems/ruby-2.3.1/gems/actionpack-5.0.0.1/lib/action_dispatch/middleware/templates/rescues/_request_and_response.html.erb Rendered /home/zedong/.rvm/gems/ruby-2.3.1/gems/actionpack-5.0.0.1/lib/action_dispatch/middleware/templates/rescues/_request_and_response.html.erb (0.7ms) Rendered /home/zedong/.rvm/gems/ruby-2.3.1/gems/actionpack-5.0.0.1/lib/action_dispatch/middleware/templates/rescues/template_error.html.erb within rescues/layout (21.5ms)

和group.rb：

class Group < ActiveRecord::Base
  belongs_to :user
  has_many :posts
  validates :title, presence: true
  has_many :group_relationships
  has_many :members, through: :group_relationships, source: :user
end

post.rb:

class Post < ApplicationRecord
  validates :content, presence: true
  belongs_to :user
  belongs_to :group

  scope :recent, -> {order("created_at DESC")}
end

因为我是第二次做这个教程，所以我将它与第一次的代码进行了比较。而且我也尝试过一个一个复制文件来寻找问题所在，但是还是不行。顺便说一句，当我想实现eidt和删除按钮时，出了点问题。

项目在这里：github

Answer 1

您需要确保 group 与 post 相关联，您可以使用 try 仅用于呈现纯内容（因此它不呈现任何内容，但不t 抛出异常）：

<td> <%= post.group.try(:title) %> </td>

和 if 控制流程以有条件地呈现链接：

<% if post.group.present? %>
  <td> <%= link_to('Edit', edit_group_post_path(post.group, post), class: "btn btn-default btn-xs") %></td>
  <td> <%= link_to('Delete', group_post_path(post.group, post), method: :delete, data: { confirm: "Are you sure?" }, class: "btn btn-default btn-xs") %></td>
<%end%>

Account::Posts#index 中的 NoMethodError

NoMethodError in Account::Posts#index

ruby-on-rails

ruby-on-rails-5