Bootstrap4 form template for rails.

_form.html.erb

<%# app/view/shared/_form.html.erb %>
<%= form_with model: record, url: url, local: true, class: 'px-4' do |form|%>
  <% elements.each do |elem|%>
    <div class="form-group form-row mb-5">
      <%= form.label elem.label, for: elem.id, class: 'col-md-3 col-lg-2 col-form-label'%>
      <div class="col-md-9 col-lg-10">
        <% if elem.type?(:collection_radio_buttons, :collection_check_boxes) %>
          <div>
            <%= form.public_send elem.type, elem.name, *elem.args, include_hidden: false do |check|%>
              <%= tag.div class: 'form-check form-check-inline', style: elem.style do%>
                <%= check.public_send elem.check_method, class: class_names('form-check-input', 'is-invalid': record.errors.include?(elem.name)) %> <%= check.label class: 'form-check-label'%>
              <%end%>
            <%end%>
          </div>
        <% elsif elem.type?(:collection_select, :grouped_collection_select) %>
          <%= form.public_send elem.type, elem.name, *elem.args, {}, class: class_names('form-control', elem.class, 'is-invalid': record.errors.include?(elem.name)), id: elem.id, style: elem.style %>
        <% else %>
          <%= form.public_send elem.type, elem.name, class: class_names('form-control', elem.class, 'is-invalid': record.errors.include?(elem.name)), id: elem.id, style: elem.style, placeholder: elem.placeholder %>
        <%end%>
        <%- if record.errors.include?(elem.name) -%>
          <ul class="list-unstyled mb-0 text-danger">
            <% record.errors.full_messages_for(elem.name).each do |err|%>
            <li><%= err %></li>
            <%end%>
          </ul>
        <%- end -%>
        <% if content_for?("form_note_for_#{elem.name}".to_sym) %>
          <div class="font-weight-light"><%= yield "form_note_for_#{elem.name}".to_sym %></div>
        <%end%>
      </div>
    </div>
  <%end%>
  <% if content_for?(:form_footer) %>
    <%= yield :form_footer %>
  <% end %>
<%end%>

element.rb

# app/models/fomrs/element.rb
class Forms::Element
  include ActiveModel::Model
  attr_accessor :type, :name, :label, :class, :args, :style, :placeholder

  def type?(*types)
    types.include?(type)
  end

  def id
    "form_element_#{name}"
  end

  def check_method
    return :radio_button if type?(:collection_radio_buttons)
    return :check_box if type?(:collection_check_boxes)
    raise 'This element is not check type.'
  end
end

form.html.erb

<%# app/view/recruit/form.html.erb %>
<% content_for :form_note_for_name do%>
  <p><%= _('ひらがなで、苗字と名前の間にスペースを空けてください。') %></p>
<% end %>

<% content_for :form_note_for_tel do%>
  <p><%= _('ハイフンやスペースは必要ありません。半角数字で入力お願いします。') %></p>
<% end %>

<% content_for :form_footer do%>
  <div class="form-group mb-5">
    <input type="submit" name="submit_recruit" value="<%= _('送信') %>" class="btn btn-outline-primary btn-block mx-auto w-50">
  </div>
<% end %>

<%= content_for :base_content do%>
  <section>
    <%= render 'layouts/small_promo', description: _('応募する'), title: _('Apply') %>
    <section class="container">
      <%= section_heading _('応募フォーム'), 3 %>
      <p><%= _('全ての項目を入力お願いします。') %></p>
      <%= render 'shares/form', record: @recruit, url: form_recruits_path, elements: [Forms::Element.new(
        type: :text_field,
        name: :name,
        label: _('氏名'),
        placeholder: 'てら　ともこ'
      ), Forms::Element.new(
        type: :email_field,
        name: :email,
        label: _('メールアドレス'),
      ), Forms::Element.new(
        type: :telephone_field,
        name: :tel,
        label: _('電話番号'),
        placeholder: '09011112222'
      ), Forms::Element.new(
        type: :number_field,
        name: :age,
        label: _('年齢'),
        style: 'width: 80px;',
        placeholder: '20'
      ), Forms::Element.new(
        type: :collection_radio_buttons,
        name: :sex,
        label: _('性別'),
        args: [Forms::Recruit::SEXES, :to_s, :to_s],
        style: 'width: 160px;'
      ), Forms::Element.new(
        type: :collection_check_boxes,
        name: :job_types,
        label: _('職種'),
        args: [Forms::Recruit::JOB_TYPES, :to_s, :to_s],
        style: 'width: 160px;'
      ), Forms::Element.new(
        type: :collection_radio_buttons,
        name: :exp,
        label: _('サロン勤務経験'),
        args: [Forms::Recruit::YES_OR_NO, :to_s, :to_s],
        style: 'width: 160px;'
      ), Forms::Element.new(
        type: :collection_select,
        name: :nail_cert,
        label: _('検定・資格'),
        args: [Forms::Recruit::NAIL_CERTS, :first, :second],
        style: 'width: 160px;'
      ), Forms::Element.new(
        type: :collection_radio_buttons,
        name: :hair_license,
        label: _('美容師免許'),
        args: [Forms::Recruit::YES_OR_NO, :to_s, :to_s],
        style: 'width: 160px;'
      )]%>
    </section>
  </section>
<%end%>