I read the doc about universal app and I read how to convert iphone app to ipad, but can I convert ipad app to iphone app?
Is there a tutorial for a universal app?
Yes .
in Xcode, select your application and select "Universal" from the device family and presto, your application is now universal.
Nils , XIB, . , .
if ( UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiomPad ) /* do something for the iPad */ else /* do something for the iPhone */
( Google): http://blog.corywiles.com/creating-a-universal-ios-app-tutorial