Ruby on Rails - # 的未定义方法`category'<Post:0x000055a44cf6bd00> 你的意思是？类别编号

Question

Error Message Screenshot I am learning Ruby on Rails in college right now and I am struggling with it.错误消息屏幕截图我现在正在大学学习 Ruby on Rails，但我正在为此苦苦挣扎。 I have a project to be finished in the next days but I cannot find out what is wrong with my code, I have tried to fix for it, I googled it already but no luck.我有一个项目要在接下来的几天内完成，但我找不到我的代码有什么问题，我试图修复它，我已经用谷歌搜索了它但没有运气。

Due to the coronavirus the educational institutions are closed and I am unable to ask my lecturer for assistance on this.由于冠状病毒，教育机构关闭，我无法向我的讲师寻求帮助。

I would appreciate if someone could help me out on this?如果有人能帮我解决这个问题，我将不胜感激？

My application is very simple, it is a place where people can post whatever they want, however, they need to choose a category and other people can comment on it.我的应用程序很简单，它是一个人们可以发布他们想要的任何内容的地方，但是，他们需要选择一个类别，其他人可以对其发表评论。

The error I am getting displayed on the browser is the below:我在浏览器上显示的错误如下：

undefined method 'category' for # #的未定义方法“类别”

Did you mean?你的意思是？ category_id类别编号

Trace of template inclusion: #模板包含的痕迹：#

app/views/layouts/_breadcrumb_nav.html.erb:21 app/views/layout/application.html.erb:16 app/views/layouts/_breadcrumb_nav.html.erb:21 app/views/layout/application.html.erb:16

Request要求

Parameters:参数：

{"id"=>"3"} {“id”=>“3”}

My code where the error is been displayed is the below:我显示错误的代码如下：

Below is the /app/views/layouts/_breadcrumb_nav.html.erb下面是/app/views/layouts/_breadcrumb_nav.html.erb

<!-- Check if there is a post present, a category is present and handle these two scenarios differently, also includes a default link back to the home page -->
<div class="inner">

  <!-- Check if the user is signed in, otherwise just show the normal link -->
  <% if account_signed_in? %>
    <%= link_to "Sign Out", destroy_account_session_path, method: :delete, class: "pull-right m-l-10" %>
    <% else %>

  <%= link_to "Account", root_path, class: "pull-right m-l-10" %>
    <% end %>

  <%= link_to "New Post", new_post_path, class: "pull-right" %>

  <%= link_to "Home", root_path %> >>

  <!-- Do not show category if category if it is new entry and has no category set yet
       check out application_helper.rb
  -->

  <% if @post.present? && !@post.new_record?
       category = @post.category
       parent = category.parent if category.present?
  %>


    <% if parent.present? %>
      <%= link_to parent.name, category_path(parent) %> >>
    <% end %>

    <%= link_to category.name, category_path(category) %> >>
    <%= @post.title %>
  <% elsif @category.present?
       parent = @category.parent
  %>
    <% if parent.present? %>
      <%= link_to parent.name, category_path(parent) %> >>
    <%end %>

      <%= @category.name %>
    <% end %>
</div>

Below is the /app/views/layouts/application.html.erb下面是/app/views/layouts/application.html.erb

<!DOCTYPE html>
<html>
  <head>
    <title>Marketplace</title>
    <%= csrf_meta_tags %>
    <%= csp_meta_tag %>

    <%= stylesheet_link_tag 'application', media: 'all' %>
    <%= javascript_pack_tag 'application' %>
  </head>

  <body>


  <div class="header" >
    <%= render "layouts/breadcrumb_nav" %>
  </div>


  <p class="notice"><%= notice %></p>


    <!-- divs for the menu -->
    <div class="main">
      <div class="main-left">
        <p><strong><%= link_to "Marketplace", root_path %></strong></p>

        <!-- Hides the Create a New Post menu once the user leaves the home page -->
        <p><%= link_to "Create a New Post", new_post_path %></p>

        <!-- User login - devise gem-->
        <p><%= link_to "User Login", new_account_session_path unless account_signed_in? %></p>

        <!-- load in categories if the user on a category page, only loads if the categories controller is being used -->
        <%= render "categories/category_sidebar"  if controller.controller_name == "categories" %>



        <% if is_home? %>
        <div class="nav-pages">
          <p><%= link_to "faqs, help", faqs_path %></p>
          <p><%= link_to "learn more about marketplace", about_path %></p>
          <p><%= link_to "avoid scams, fraud, safety tips", fraud_path %></p>
          <p><%= link_to "terms of use", terms_path %></p>
        </div>
        <% end %>

      </div>
      <div class="main-right">

    <%= yield %>

      </div>
    </div>

  </body>
</html>

Below is the /app/models/post.rb下面是/app/models/post.rb

class Post < ApplicationRecord
  # Setting up the relationship in the DB
  belongs_to :parent, class_name: "Category", optional: true
  has_many :subcategories, class_name: "Category", foreign_key: :parent_id, dependent: :destroy
  has_many :posts
end

I have a little bit of knowledge of Java and Ruby on Rails is killing me and I hope you can help me out.我对 Java 和 Ruby on Rails 有一点了解，我希望你能帮助我。

Many thanks Richard非常感谢理查德

Answer 1

I'm guessing your trying to to build something like a breadcrumb navigation that looks something like this:我猜您正在尝试构建类似如下所示的面包屑导航：

Authors >> French >> Albert Camus

Start by setting up the associations:首先设置关联：

class Post < ApplicationRecord
  belongs_to :category
  # lets you call post.parent_category without dealing with nil errors
  has_one :parent_category, 
    through: :category
end

class Category < ApplicationRecord
  has_many :posts
  belongs_to :parent_category, 
    class_name: 'Category',
    optional: true
end

Then DRY the code into a partial instead of making soup out of your ERB.然后将代码干燥成部分代码，而不是用 ERB 制作汤。

# app/views/posts/_breadcrumbs.html.erb
<div class="breadcrumbs">
  <% [post.parent_category, post.category].compact.each do |c| %>
    <%= link_to c.name, c %> &raquo;
  <% end %>
  <%= post.name %>
</div>

» looks like ».好像 ”。 If you actually want to use >> you need to escape it >>如果你真的想使用>>你需要转义它>> or use <%= content_tag(:span, '>>') %> as > has special significance in HTML.或使用<%= content_tag(:span, '>>') %>因为>在 HTML 中具有特殊意义。

Then render the partial in the view where you want it:然后在您想要的视图中渲染部分：

# app/views/posts/show.html.erb
<%= render partial: 'breadcrumbs', post: @post %>

Ruby on Rails - # 的未定义方法`category'<Post:0x000055a44cf6bd00> 你的意思是？类别编号

问题描述

1 个解决方案

解决方案1
0 2020-03-20 02:23:07

Ruby on Rails - # 的未定义方法`category&#39;<Post:0x000055a44cf6bd00> 你的意思是？ 类别编号

问题描述

1 个解决方案

解决方案1 0 2020-03-20 02:23:07

Ruby on Rails - # 的未定义方法`category'<Post:0x000055a44cf6bd00> 你的意思是？类别编号

解决方案1
0 2020-03-20 02:23:07