在视图控制器中添加多个导航控制器？

I'm trying to acheive a dual-tabBar app for the iPhone and using the following code for a base class view controller to add several navigation controllers inside the view controller (see code below). But the problem is: No subviews are added to self.view, despite them being initialized earlier. Any ideas?I'm trying to acheive a dual-tabBar app for the