Bootstrap-select不扩展

Question

我遇到了selectpicker下拉列表的问题。点击后我无法获得下拉菜单。 以下是我的文件：

查看：

<div class="form-group set-up-down">
            <%= f.label :pricing_style_id %><br>
            <%= f.select 'pricing_style_id', options_from_collection_for_select(@labs_pricing_style, :id, :name),{:include_blank => '-Choose Starting Price Sheet-'},class:'selectpicker'%>
            <p id="pricingstyleError" style="display: none; color: red;">Please enter a pricing style for this new pricesheet.</p>
          </div>

的application.js：

//= require jquery
//= require jquery_ujs
//= require jquery.turbolinks
//= require bootstrap-colorpicker.min
//= require bootstrap-datetimepicker.min
//= require bootstrap-select.min
//= require bootstrap-switch
//= require bootstrap-switch.min
//= require bootstrap-tagsinput
//= require bootstrap
//= require jquery-1.12.1.min
// require_tree .

application.css：

 *= require_tree .
 *= require_self

任何帮助将不胜感激。提前谢谢你。