title: Rails fields_for update not working (deleting the parent object)
body: <p>I have <code>fields_for</code> form <strong>for update</strong> like below:</p>
  
  <pre><code>  &lt;%= form_for @cuisine, url: {action: "update" } do |f| %&gt;
      &lt;%= f.text_area :name %&gt;
  
      &lt;% @cuisine.ingredients.each do |ing| %&gt;     
        &lt;%= f.fields_for ing do |ingredient_fields|%&gt;
          &lt;%= ingredient_fields.text_area :name, :value=&gt; ing.name %&gt;
          &lt;%= ingredient_fields.hidden_field :_destroy%&gt;
          &lt;%= link_to_remove_fields 'Remove this ingredient', f %&gt;
        &lt;% end %&gt;
      &lt;% end %&gt;
  
    &lt;% end %&gt;
  </code></pre>
  
  <p>my cuisines_controller:</p>
  
  <pre><code>def update
    @cuisine = Cuisine.find(params[:id])
    if @cuisine.update_attributes(cuisine_params)
       redirect_to root_path
    else
       redirect_to edit_cuisine_path
    end
  end
  </code></pre>
  
  <p>Though this shows the form correctly (showing forms filled with @cuisine and its ingredients' info), after reloading the page the @cuisine object gets deleted even when I don't push the submit button.</p>
  
  <p>Any idea what's going on or how to update nested attributes using <code>fields_for</code>?</p>
  
  <p>Thanks in advance.</p>