call async asihttp in different view controller
<p>I try to use UINavigationController to navigate from one view controller to another.
In both viewController , the viewWillAppear</p>

<p>I call asihttp using async mode.</p>

<p>but this always cause the app crash.</p>

<p>I try to use the function of asihttp '[request cancel]'
in the wiewWillDisaaoear, but the error still exist</p>

<p>Welcome any comment</p>
