[Beginning Rails 6] Listing 8-20. Modified app/views/articles/_form.html.erb

_form.html.erb

<%= form_with(model: article, local: true) do |form| %>
  <% if article.errors.any? %>
    <div id="error_explanation">
      <h2><%= pluralize(article.errors.count, "error") %> prohibited this article from being saved:</h2>

      <ul>
        <% article.errors.full_messages.each do |message| %>
          <li><%= message %></li>
        <% end %>
      </ul>
    </div>
  <% end %>

  <div class="field">
    <%= form.label :title %>
    <%= form.text_field :title %>
  </div>

  <div class="field">
    <%= form.label :location %>
    <%= form.text_field :location %>
  </div>

  <div class="field">
    <%= form.collection_check_boxes(:category_ids, Category.all, :id, :name) do |b| %>
      <% b.label { b.check_box + b.text } %>
    <% end %>
  </div>

  <div class="field">
    <%= form.label :excerpt %>
    <%= form.text_field :excerpt %>
  </div>

  <div class="field">
    <%= form.label :body %>
    <%= form.text_area :body %>
  </div>

  <div class="field">
    <%= form.label :published_at %>
    <%= form.datetime_select :published_at %>
  </div>

  <div class="actions">
    <%= form.submit %>
  </div>
<% end %>