title: render method url dosen't match original url
body: <p>Let's say i have a form which is at:</p>
  
  <blockquote>
    <p>/categories/new</p>
  </blockquote>
  
  <p>When form input is invalid I call render. Classic example:</p>
  
  <pre><code>  def create
      @category = Category.new(category_params)
      if @category.save
        flash[:success] = 'Category successfully created.'
        redirect_to @category
      else
        render 'new'
      end
    end
  </code></pre>
  
  <p>My question is, why site path after call to render is just: </p>
  
  <blockquote>
    <p>/categories</p>
  </blockquote>
  
  <p>and not:</p>
  
  <blockquote>
    <p>/categories/new</p>
  </blockquote>
  
  <p>As I understand 'new' form should be rendered on the same page and those two paths clearly aren't the same.</p>
  
  <p>As commenters suggested here is additional info:</p>
  
  <p>related routes:</p>
  
  <pre><code>  resources :categories do
      resources :topics, name_prefix: 'category_',
                         except: [:index, :show, :edit, :update, :destroy]
    end
  </code></pre>
  
  <p>category new action:</p>
  
  <pre><code>  def new
      @category = Category.new
    end
  </code></pre>