title: ARC Retain Cycle appears after updating to iOS 6.1
body: <p>After updating to iOS 6.1, I'm getting this warning in AFImageRequestOperation.m and AFHTTPClient.m from AFNetworking framework:</p>
  
  <blockquote>
    <p>Capturing 'operation' strongly in this block is likely to lead to a
    retain cycle</p>
  </blockquote>
  
  <p>Based on <a href="https://stackoverflow.com/a/12802487/1449151">this answer,</a> I can fix a retain cycle in ARC by using __weak variables. It is also says </p>
  
  <blockquote>
    <p>Block will be retained by the captured object</p>
  </blockquote>
  
  <p>Does anyone know how to solve this?</p>
  
  <p>Thanks.</p>