title: Hide bottom bar on demand
body: <p>I have a UINavigationController inside a UITabBarController. I'm presenting a sort of popover view using a semi-transparent UIView, but am not calling <code>presentModalViewController</code> or any of the usual methods. I know about <code>hidesBottomBarWhenPushed</code>, but is there a way I can hide the bottom bar (or even betterm slide it out) on demand (just before my subView is added to the navigationController's top view)?</p>