Rails集合選擇類別和子類別

Question

我在設法實現以下方法時遇到了麻煩：我想將循環放在select field下面，並且只能選擇子類別。

@categories = Category.where(ancestry: nil)
@subcategories = Category.where("ancestry is NOT NULL and name != ''")

<% @categories.each do |category| %>
    <%= category.name %>
      <% unless category.children.empty? %>
        <% category.children.each do |subcategory| %>
          <%= subcategory.name %>
        <% end %>
     <% end %>
<% end %>

我得到以下子類別：

<%= form.collection_select(:category_id, @ subcategories, :id, :name) %>

但是，如何在選擇字段中按順序放置類別（不可選擇）和子類別（可選擇）呢？

Answer 1

<%= form.grouped_collection_select :category_id, Category.roots.order(:name), :children, :name, :id, :name, {:include_blank => true}, {class: "", :multiple => true } %>