title: Rails, polymorphic association. Destroy with "touch: true", useless steps
body: <p>I'm on <strong>Rails 5</strong>.</p>
  
  <p>I have a polymorphic association like this:</p>
  
  <p><em>models/enjoy_level.rb</em>:</p>
  
  <pre><code>class EnjoyLevel &lt; ApplicationRecord
    belongs_to :enjoyable, polymorphic: true, touch: true, optional: true
  end
  </code></pre>
  
  <p><em>models/mother.rb</em>:</p>
  
  <pre><code>class Mother &lt; ApplicationRecord
    has_one :enjoy_level, as: :enjoyable, dependent: :destroy
  
    accepts_nested_attributes_for :enjoy_level
  end
  </code></pre>
  
  <p>If I destroy one <code>mother</code> (which have <code>touch: true</code> option) it still:</p>
  
  <ul>
  <li>destroy the <code>enjoy_level</code> one before;</li>
  <li>set <code>Mother</code> <code>update_at</code> to now();</li>
  <li>and finally destroy this <code>Mother</code> record one.</li>
  </ul>
  
  <p><strong>The first and second steps are useless</strong>, right?</p>
  
  <p>Where am I wrong?</p>