title: What does rails do after redirect_to or render in controller?
body: <p>For example, I have something like this in my controller:</p>
  <pre><code>def save
    ...
    render 'error' if user.nil?
    @cast = user.cast
    render 'cast'
  end
  </code></pre>
  <p>I have nil: no method error here (in <code>user.cast</code>). But if I use <code>redirect_to</code> instead of <code>render</code>, everything works perfectly.</p>
  <p>It seems like Rails doesn't stop their executive stack after <code>render</code>, but stops after <code>redirect_to</code>. Doesn't it?</p>