如何在具有多方向关联的Rails中创建三重嵌套对象

class A < ApplicationRecord
  has_many :a_bs
  has_many :bs, through: :a_bs
  accepts_nested_attributes_for :bs

  has_many :a_cs
  has_many :cs, through: :a_cs
  accepts_nested_attributes_for :cs
end

class AController < ApplicationController
  def a_params
    params.require(:a).permit(:name, bs_attributes: [:id, :name], cs_attributes: [:id, :name])
  end
end

<%= form_with(model: @a, local: true) do |form| %>
  <%= form.label :name %>
  <%= form.text_field :name %>

  <%= form.fields_for :bs do |b_fields| %>
    <%= b_fields.label :name %>
    <%= b_fields.text_field :name %>
  <% end %>

  <%= form.fields_for :cs do |c_fields| %>
    <%= c_fields.label :name %>
    <%= c_fields.text_field :name %>
  <% end %>

  <%= form.submit %>
<% end %>

class AController < ApplicationController
  def create
    @a = A.new(a_params)
    @a.bs.build
    @a.cs.build
    if @a.save
      redirect_to @a
    else
      render 'new'
    end
  end
end