title: Conditional callbacks scope
body: <p>I have in my model some conditional callbacks</p>
  
  <pre><code>before_create :save_tempfile, :if =&gt; :has_stream_content?
  after_create :add_track, :if =&gt; :has_stream_content?
  before_update :add_track, :if =&gt; :has_stream_content?
  </code></pre>
  
  <p>Is there a rails way to organize a conditional callback scope? Smth like this:</p>
  
  <pre><code>before_create :save_tempfile; after_create, before_update :add_track, :if =&gt; :has_stream_content?
  </code></pre>