1- 我安装了 gem bootstrap_form
2- 我在 application.css 中写了那行*= require bootstrap_form before the */
3- 在我的 html.erb
<%= bootstrap_form_for(@guardian, :url => student_guardians_path(@student),
html: { class: 'form-horizontal' },
method: :post) do |f| %>
我收到以下错误:undefined method
bootstrap_form_for' for #<#:0xb31a80c>`