Ruby on rails 将类别子类别关系列至第n级

我有一个categories表，其中有一个parent_id列，下面是categories模型

class Category < ActiveRecord::Base

  has_many :subcategories, :class_name => "Category", :foreign_key => :parent_id, :dependent => :destroy
  has_one :parent, :class_name => "Category", :primary_key => :parent_id, :foreign_key => :id
end

---

您可以制作包含重复标记的分部，例如：

<% @categories.each do |category| %>
        <ul>
          <% if category.parent_id.blank? %>
            <li class="big-bold"><%= category.name %> <%= link_to "Edit", edit_admin_category_path(category), :class => "btn btn-primary btn-xs" %> <%= link_to "Delete", admin_category_path(category), :method => 'delete', :class => "btn btn-danger btn-xs", data: { confirm: 'Are you sure?' } %>
              <% if category.subcategories.present? %>
                <%= render partial: 'subcategory', locals: {subcategories: category.subcategories} %>
              <% end %>
                </ul>
              <% end %>
            </li>
          <% end %>
        </ul>
  <% end %>

<ul>
  <% subcategories.each do |sub| %>
    <li class="top-clear"><%= sub.name %> <%= link_to "Edit", edit_admin_category_path(sub), :class => "btn btn-primary btn-xs" %> <%= link_to "Delete", admin_category_path(sub), :method => 'delete', :class => "btn btn-danger btn-xs", data: { confirm: 'Are you sure?' } %>
  <% if sub.subcategories.present? %>
    <%= render partial: 'subcategory', locals: {subcategories: sub.subcategories} %>
  <% end %>

</li>
  <% end %>
</ul>

---

可能是因为你在懒洋洋地加载记录。不，我在使用这个，

@categories=Category.select（'id，name，parent\u id，slug'）。包括（：subcategories）

你能发布有问题的数据库查询日志吗？我会说这是因为

Category.subcategories.present？

调用视图。我想如果您在模型中添加

includes:：subcategories

到

has\u many:subcategories

，可以减少查询数量。

<% @categories.each do |category| %>
        <ul>
          <% if category.parent_id.blank? %>
            <li class="big-bold"><%= category.name %> <%= link_to "Edit", edit_admin_category_path(category), :class => "btn btn-primary btn-xs" %> <%= link_to "Delete", admin_category_path(category), :method => 'delete', :class => "btn btn-danger btn-xs", data: { confirm: 'Are you sure?' } %>
              <% if category.subcategories.present? %>
                <%= render partial: 'subcategory', locals: {subcategories: category.subcategories} %>
              <% end %>
                </ul>
              <% end %>
            </li>
          <% end %>
        </ul>
  <% end %>

<ul>
  <% subcategories.each do |sub| %>
    <li class="top-clear"><%= sub.name %> <%= link_to "Edit", edit_admin_category_path(sub), :class => "btn btn-primary btn-xs" %> <%= link_to "Delete", admin_category_path(sub), :method => 'delete', :class => "btn btn-danger btn-xs", data: { confirm: 'Are you sure?' } %>
  <% if sub.subcategories.present? %>
    <%= render partial: 'subcategory', locals: {subcategories: sub.subcategories} %>
  <% end %>

</li>
  <% end %>
</ul>