在表单中选择多个引用

Question

我有一个MenuPizza模型连接到ToppingsModel的连接表：

class MenuPizza < ActiveRecord::Base
  has_many :pizza_toppings
  has_many :toppings, through: :pizza_toppings
end

class PizzaTopping < ActiveRecord::Base
  belongs_to :menu_pizza
  belongs_to :topping
end

class Topping < ActiveRecord::Base
  has_many :menu_pizzas, through: :pizza_toppings

  has_many :pizza_toppings, inverse_of: :topping
end

当用户创建新的MenuPizza时，他们应该能够从包含数据库中已有的所有浇头的下拉列表中选择一个浇头。他们应该能够为多个浇头做到这一点。

= form_for @menu_pizza do |f|
  - if @menu_pizza.errors.any?
    #error_explanation
      %h2 = pluralize(@menu_pizza.errors.count, 'error') prohibted this post from being saved

  .field
    = f.label :name
    = f.text_area :name

    = f.label :description
    = f.text_area :description

    = f.select(:topping_ids, @toppings)

    = f.submit 'Add Toppings', name: 'add-toppings'

我的问题是，如何提交对配料的多个参考？我试过了：

= f.select(:topping_ids, @toppings)
= f.select(:topping_ids, @toppings)

但是只提交了最后选择的顶部。