class Area < ApplicationRecord
  def self.options_data
    self.order("id ASC").collect{|record| [record.name, record.id]}
  end
end

<%= form_tag "", method: :GET, class: "mt-4" do %>
  <%= select_tag "area_id", options_for_select(Area.options_data, params[:area_id]), include_blank: "-- 所有国家 --" %>
    --"} %>
  <%= submit_tag "查询", class: "btn" %>
<% end %>

class ProductCategory < ApplicationRecord
  # Used for f.select tag
  def self.options_data
    order("id ASC").collect { |record| [record.name, record.id] }
  end
end

<%= form.select :product_category_id, ProductCategory.options_data, {}, {class: ""} %>

<%= f.collection_select :product_category_id, PostCategory.all, :id, :name, class: "mt-1 block w-full" %>