Trouble while moving a UITabBar object

I face trouble while i try to move my UITabBar object in a UIViewController.

Whenever I change the position of my UITabBar object by changing its frame.origin attribut, the object is correctly displayed at the position, however I lost the interface: whenever I select the UITabBarItem, the 'didSelect' method is not called anymore.

If I don't change its frame.origin attribut, the 'didSelect' method is called when I select an UITabBarItem. Is that a known issue?

I need to move this object programmatically, as while rotating the device, it does rotate but it doesn't stay at the bottom of the view. Any clue on how to fix it?

Thanks