Hm. While writing subject, I've found that this is impossible (according to this thread).
My goal is pretty simple: I have popover and button inside it. I want to show something bigger than current size of popover on button touchedUpInside, so I need resize popover. But since I can't get the reference to the popover, I need to keep reference to popover's "super view controller". That's just ugly.
So now I'm looking for some more elegant solutions.
UPDATE: That's ugly because I've ended with that expression:
[(UIPopoverController*)[[(AppDelegate*)[[UIApplication sharedApplication] delegate] calendarViewController]
performSelector: @selector(popover)]
setPopoverContentSize:viewFrame.size animated: YES];
Just to resize simple popover :(