title: Rails - simple_form, include a named blank object in a collection on new and edit
body: <p>I have a simple_form  which I am trying to get to always include a blank item in it, as a 'nil' value in that field has a special meaning in this database.
  In order to make it more obvious for end users, I also want to title it with something along the lines of "(select if none)".</p>
  
  <p>I'm currently doing this, but it only inserts the 'blank' item when creating a new object, not when editing one.</p>
  
  <pre><code># _child_form.html.erb
  
  &lt;%= simple_form_for @child do |f| %&gt;
    &lt;%= f.input :first_name %&gt;
    &lt;%= f.input :last_name %&gt;
    &lt;%= f.association :parent, :collection =&gt; @parents, :prompt =&gt; "(select if none)" %&gt;
  
    &lt;%= f.button.submit %&gt;
  &lt;% end %&gt;
  </code></pre>
  
  <p>.</p>
  
  <pre><code># child_controller.rb
  
  def new
    @child = Child.new
    @parents = Parent.all
  end
  
  def edit
    @child = Child.find(params[:id])
    @parents = Parent.all
  end
  </code></pre>