UIPopoverController and Modal View Controllers - iOS Programming: The Big Nerd Ranch Guide - page 396

Universalizing Homepwner
Open Homepwner.xcodeproj and select the Homepwner project from the project nav-
igator. Then select the Homepwner target in the editor area. In the Summary pane, change
the Devices pop-up to Universal ( Figure 13.2 ).
Figure 13.2 Universalizing Homepwner
That was it. Homepwner now runs natively on the iPad. Click on the Scheme pop-up but-
ton next to the Run button. You'll see that there is now an iPad Simulator option. Select
this option and build and run the application.
The ItemsViewController view looks great on the iPad, but if you select a row,
you'll see that the DetailViewController 's interface could use some work. (Also,
tapping the button to take a picture throws an exception. We'll fix this shortly.)
One way to improve the looks of the DetailViewController 's interface on the iPad
is to change the autoresizing masks of the subviews in DetailViewController.xib
so that when its view is resized to fit the iPad, all of the subviews are organized nicely. This
is what you did when you universalized your HeavyRotation application.
Another way is to create two completely independent XIB files: one for the iPhone device
family and the other for the iPad. This is most useful when you want to have a different in-
terface on the iPad that takes advantage of the additional screen space. To do this, you
name the iPad-specific XIB file the same as the iPhone version with an added ~ipad suf-
fix, like DetailViewController~ipad.xib . Remember to recreate the entire view
hierarchy and re-establish connections in the iPad version of the XIB file.
When you create separate XIB files for the two device families and use the ~ipad suffix,
you do not need to write any extra code to load the appropriate XIB file. Every