数据库中没有记录的Rails form_for复选框验证

<%= form_for @model do |f| %>
  <%= f.collection_check_boxes :category_ids, Category.all, :id, :name %>
  <%= f.submit %>
<% end %>

class ModelsController < ApplicationController
  def create
    @model = Model.new(model_params)
    if @model.save
      # 保存成功的逻辑
    else
      # 保存失败的逻辑
    end
  end

  private

  def model_params
    params.require(:model).permit(category_ids: [])
  end
end

class Model < ApplicationRecord
  validate :categories_selected

  def categories_selected
    errors.add(:base, "Please select at least one category") if category_ids.empty?
  end
end