Question

The manual (Listing 5-2) says that the split view controller can be added to the UIWindow like thus:

[window addSubview:splitVC.view];

However, in an example code I have seen the following to be working perfectly fine.

[window setRootViewController:splitVC];

What is the difference between these?

Answer 1

They both do the same thing in this case but there are differences between addSubview and setRootViewController. addSubView is a method of UIView whereas UIWindow inherits from UIView and therefore the method, while its rootviewcontroller property is from UIWindow class. But the differences in the methods are

• addSubview adds the view into the callers view hierarchy and the
  calling object retains ownership.

• setRootViewController sets the view as the windows only view or main
  view, if you will. An additional point is that it removes all subviews,if any, while addSubView does not do that.