lesson作成画面

%h1 Lesson作成
= form_for(@lesson) do |f|
  .field
    = f.label :part, "Lesson番号(大問)"
    %br
    = f.number_field :part

  .field
    = f.label :number, "Lesson番号(小問)"
    %br
    = f.number_field :number

  .field
    = f.label :subject_id, "割り当てる課題"
    = f.collection_select :subject, Subject.all, :id, :title
    %br
    %br

  .actions
    = f.submit "保存する"

- flash.each do |type, msg|
  %div{class: "alert alert-#{type}"}= simple_format(msg)

= debug(params) if Rails.env.development?

多分使いませんがとっておきます