Unsolved iOS: OpenInMenu from Qt UI (UIDocumentInteractionController)

[ekkescorner]

just working on some more options for my sharing example app.
to display the native iOS OpenIn... Dialog:

UIDocumentInteractionController* documentInteractionController = nil;
documentInteractionController = [UIDocumentInteractionController interactionControllerWithURL:nsFileUrl];

UIViewController* qtUIViewController = [[[[UIApplication sharedApplication]windows] firstObject]rootViewController];
if(qtUIViewController!=nil)
{
        [documentInteractionController retain];
        if(![documentInteractionController presentOpenInMenuFromRect:CGRectZero inView: qtUIViewController.view animated: true])
        {
            // do something
        }
    }
}

I had to explicitely retain the UIDocumentInteractionController - without this the URL gets lost and I cannot open the file in another App.
I'm not so experienced with Obj-C, so my question is: do I also have to explicitely release the Controller - and if yes where should this be done.

thx