From the docs of UITabBarController:
If the root view controller is a navigation controller, the tab bar controller makes further adjustments to the size of the displayed navigation content so that it does not overlap the tab bar. Any views you display in a tab bar interface should therefore have their autoresizingMask property set to resize the view appropriately under any conditions.
so, if I don't use any nibs, which autoresizing masks must I use here?